barchat(n) manual page

Table of Contents

## Name

barchart - Bar chart for plotting X-Y coordinate data.

## Synopsis

barchart pathName ?option value?...

## Description

The barchart command creates a bar chart for plotting two-dimensional data (X-Y coordinates). A bar chart is a graphic means of comparing numbers by displaying bars of lengths proportional to the y-coordinates of the points they represented. The bar chart has many configurable components: coordinate axes, elements, legend, grid lines, cross hairs, etc. They allow you to customize the look and feel of the graph.

## Introduction

The barchart command creates a new window for plotting two-dimensional data (X-Y coordinates), using bars of various lengths to represent the data points. The bars are drawn in a rectangular area displayed in the center of the new window. This is the plotting area. The coordinate axes are drawn in the margins surrounding the plotting area. By default, the legend is drawn in the right margin. The title is displayed in top margin.

A barchart widget has several configurable components: coordinate axes, data elements, legend, grid, cross hairs, pens, postscript, and annotation markers. Each component can be queried or modified.

axis

  Up to four coordinate axes (two X-coordinate and two Y-coordinate axes) can be displayed, but you can create and use any number of axes. Axes control what region of data is displayed and how the data is scaled. Each axis consists of the axis line, title, major and minor ticks, and tick labels. Tick labels display the value at each major tick.

crosshairs
  Cross hairs are used to position the mouse pointer relative to the X and Y coordinate axes. Two perpendicular lines, intersecting at the current location of the mouse, extend across the plotting area to the coordinate axes.
element
  An element represents a set of data to be plotted. It contains an x and y vector of values representing the data points. Each data point is displayed as a bar where the length of the bar is proportional to the ordinate (Y-coordinate) of the data point. The appearance of the bar, such as its color, stipple, or relief is configurable.

  A special case exists when two or more data points have the same abscissa (X-coordinate). By default, the bars are overlayed, one on top of the other. The bars are drawn in the order of the element display list. But you can also configure the bars to be displayed in two other ways. They may be displayed as a stack, where each bar (with the same abscissa) is stacked on the previous. Or they can be drawn side-by-side as thin bars. The width of each bar is a function of the number of data points with the same abscissa.

grid
  Extends the major and minor ticks of the X-axis and/or Y-axis across the plotting area.
legend
  The legend displays the name and symbol of each data element. The legend can be drawn in any margin or in the plotting area.
marker
  Markers are used annotate or highlight areas of the graph. For example, you could use a text marker to label a particular data point. Markers come in various forms: text strings, bitmaps, connected line segments, images, polygons, or embedded widgets.
pen
  Pens define attributes for elements. Data elements use pens to specify how they should be drawn. A data element may use many pens at once. Here the particular pen used for a data point is determined from each element's weight vector (see the element's -weight and -style options).
postscript
  The widget can generate encapsulated PostScript output. This component has several options to configure how the PostScript is generated.

## Syntax

`barchart pathName ?option value?...
`

The barchart command creates a new window pathName and makes it into a barchart widget. At the time this command is invoked, there must not exist a window named pathName, but pathName's parent must exist. Additional options may be specified on the command line or in the option database to configure aspects of the graph such as its colors and font. See the configure operation below for the exact details about what option and value pairs are valid.

If successful, barchart returns the path name of the widget. It also creates a new Tcl command by the same name. You can use this command to invoke various operations that query or modify the graph. The general form is:

`pathName operation ?arg?...
`

Both operation and its arguments determine the exact behavior of the command. The operations available for the graph are described in the BARCHART OPERATIONS section.

The command can also be used to access components of the graph.

`pathName component operation ?arg?...
`

The operation, now located after the name of the component, is the function to be performed on that component. Each component has its own set of operations that manipulate that component. They will be described below in their own sections.

## Example

The barchart command creates a new bar chart.
`# Create a new bar chart. Plotting area is black.
barchart .b -plotbackground black
`

A new Tcl command .b is created. This command can be used to query and modify the bar chart. For example, to change the title of the graph to "My Plot", you use the new command and the configure operation.
`# Change the title.
.b configure -title "My Plot"
`

To add data elements, you use the command and the element component.
`# Create a new element named "e1"
.b element create e1 \
`` `` -xdata { 1 2 3 4 5 6 7 8 9 10 } \
`` `` -ydata { 26.18 50.46 72.85 93.31 111.86 128.47 143.14
`` `` `` `` 155.85 166.60 175.38 }
`

The element's X-Y coordinates are specified using lists of numbers. Alternately, BLT vectors could be used to hold the X-Y coordinates.
`# Create two vectors and add them to the barchart.
vector xVector yVector
xVector set { 1 2 3 4 5 6 7 8 9 10 }
yVector set { 26.18 50.46 72.85 93.31 111.86 128.47 143.14 155.85
`` `` 166.60 175.38 }
n.b element create e1 -xdata xVector -ydata yVector
`

The advantage of using vectors is that when you modify one, the graph is automatically redrawn to reflect the new values.
`# Change the y coordinate of the first point.
set yVector(0) 25.18
`

An element named e1 is now created in .b. It is automatically added to the display list of elements. You can use this list to control in what order elements are displayed. To query or reset the element display list, you use the element's show operation.
`# Get the current display list
set elemList [.b element show]
# Remove the first element so it won't be displayed.
.b element show [lrange $elemList 0 end]
`

The element will be displayed by as many bars as there are data points (in this case there are ten). The bars will be drawn centered at the x-coordinate of the data point. All the bars will have the same attributes (colors, stipple, etc). The width of each bar is by default one unit. You can change this with using the -barwidth option.
`# Change the scale of the x-coordinate data
xVector set { 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 }
# Make sure we change the bar width too.
.b configure -barwidth 0.2
`

The height of each bar is proportional to the ordinate (Y-coordinate) of the data point.

If two or more data points have the same abscissa (X-coordinate value), the bars representing those data points may be drawn in various ways. The default is to overlay the bars, one on top of the other. The ordering is determined from the of element display list. If the stacked mode is selected (using the -barmode configuration option), the bars are stacked, each bar above the previous.
`# Display the elements as stacked.
.b configure -barmode stacked
`

If the aligned mode is selected, the bars having the same x-coordinates are displayed side by side. The width of each bar is a fraction of its normal width, based upon the number of bars with the same x-coordinate.
`# Display the elements side-by-side.
.b configure -barmode aligned
`

By default, the element's label in the legend will be also e1. You can change the label, or specify no legend entry, again using the element's configure operation.
`# Don't display "e1" in the legend.
.b element configure e1 -label ""
`

You can configure more than just the element's label. An element has many attributes such as stipple, foreground and background colors, relief, etc.
`.b element configure e1 -fg red -bg pink \
`` `` -stipple gray50
`

Four coordinate axes are automatically created: x, x2, y, and y2. And by default, elements are mapped onto the axes x and y. This can be changed with the -mapx and -mapy options.
`# Map "e1" on the alternate y axis "y2".
.b element configure e1 -mapy y2
`

Axes can be configured in many ways too. For example, you change the scale of the Y-axis from linear to log using the axis component.
`# Y-axis is log scale.
.b axis configure y -logscale yes
`

One important way axes are used is to zoom in on a particular data region. Zooming is done by simply specifying new axis limits using the -min and -max configuration options.
`.b axis configure x -min 1.0 -max 1.5
.b axis configure y -min 12.0 -max 55.15
`

To zoom interactively, you link theaxis configure operations with some user interaction (such as pressing the mouse button), using the bind command. To convert between screen and graph coordinates, use the invtransform operation.
`# Click the button to set a new minimum
bind .b <ButtonPress-1> {
%W axis configure x -min [%W axis invtransform x %x]
%W axis configure x -min [%W axis invtransform x %y]
}
`

By default, the limits of the axis are determined from data values. To reset back to the default limits, set the -min and -max options to the empty value.
`# Reset the axes to autoscale again.
.b axis configure x -min {} -max {}
.b axis configure y -min {} -max {}
`

By default, the legend is drawn in the right margin. You can change this or any legend configuration options using the legend component.
`# Configure the legend font, color, and relief
.b legend configure -position left -relief raised \
`` `` -font fixed -fg blue
`

To prevent the legend from being displayed, turn on the -hide option.
`# Don't display the legend.
.b legend configure -hide yes
`

The barchart has simple drawing procedures called markers. They can be used to highlight or annotate data in the graph. The types of markers available are bitmaps, polygons, lines, or windows. Markers can be used, for example, to mark or brush points. For example there may be a line marker which indicates some low-water value. Markers are created using the marker operation.
`# Create a line represent the low water mark at 10.0
.b marker create line -name "low_water" \
`` `` -coords { -Inf 10.0 Inf 10.0 } \
`` `` -dashes { 2 4 2 } -fg red -bg blue
`

This creates a line marker named low_water. It will display a horizontal line stretching across the plotting area at the y-coordinate 10.0. The coordinates "-Inf" and "Inf" indicate the relative minimum and maximum of the axis (in this case the x-axis). By default, markers are drawn last, on top of the bars. You can change this with the -under option.
`# Draw the marker before elements are drawn.
.b marker configure low_water -under yes
`

You can add cross hairs or grid lines using the crosshairs and grid components.
`# Display both cross hairs and grid lines.
.b crosshairs configure -hide no -color red
.b grid configure -hide no -dashes { 2 2 }
`

Finally, to get hardcopy of the graph, use the postscript component.
`# Print the bar chart into file "file.ps"
.b postscript output file.ps -maxpect yes -decorations no
`

This generates a file file.ps containing the encapsulated PostScript of the graph. The option -maxpect says to scale the plot to the size of the page. Turning off the -decorations option denotes that no borders or color backgrounds should be drawn (i.e. the background of the margins, legend, and plotting area will be white).

## Syntax

`barchart pathName ?option value?...
`

The barchart command creates a new window pathName and makes it into a barchart widget. At the time this command is invoked, there must not exist a window named pathName, but pathName's parent must exist. Additional options may may be specified on the command line or in the option database to configure aspects of the bar chart such as its colors and font. See the configure operation below for the exact details as to what option and value pairs are valid.

If successful, barchart returns pathName. It also creates a new Tcl command pathName. This command may be used to invoke various operations to query or modify the bar chart. It has the general form:

`pathName operation ?arg?...
`

Both operation and its arguments determine the exact behavior of the command. The operations available for the bar chart are described in the following section.

## Barchart Operations

pathName bar elemName ?option value?...
  Creates a new barchart element elemName. It's an error if an element elemName already exists. See the manual for barchart for details about what option and value pairs are valid.
pathName cget option
  Returns the current value of the configuration option given by option. Option may be any option described below for the configure operation.
pathName configure ?option value?...
  Queries or modifies the configuration options of the graph. If option isn't specified, a list describing the current options for pathName is returned. If option is specified, but not value, then a list describing option is returned. If one or more option and value pairs are specified, then for each pair, the option option is set to value. The following options are valid.

-background color
  Sets the background color. This includes the margins and legend, but not the plotting area.
-barmode mode
  Indicates how related bar elements will be drawn. Related elements have data points with the same abscissas (X-coordinates). Mode indicates how those segments should be drawn. Mode can be infront, aligned, overlap, or stacked. The default mode is infront.

infront
  Each successive segment is drawn in front of the previous.
stacked
  Each successive segment is stacked vertically on top of the previous.
aligned
  Segments is displayed aligned from right-to-left.
overlap
  Like aligned but segments slightly overlap each other.

-barwidth value
  Specifies the width of the bars. This value can be overrided by the individual elements using their -barwidth configuration option. Value is the width in terms of graph coordinates. The default width is 1.0.
-borderwidth pixels
  Sets the width of the 3-D border around the outside edge of the widget. The -relief option determines if the border is to be drawn. The default is 2.
-bottommargin pixels
  Specifies the size of the margin below the X-coordinate axis. If pixels is 0, the size of the margin is selected automatically. The default is 0.
-bufferelements boolean
  Indicates whether an internal pixmap to buffer the display of data elements should be used. If boolean is true, data elements are drawn to an internal pixmap. This option is especially useful when the graph is redrawn frequently while the remains data unchanged (for example, moving a marker across the plot). See the SPEED TIPS section. The default is 1.
-cursor cursor
  Specifies the widget's cursor. The default cursor is crosshair.
-font fontName
  Specifies the font of the graph title. The default is *-Helvetica-Bold-R-Normal-*-18-180-*.
-halo pixels
  Specifies a maximum distance to consider when searching for the closest data point (see the element's closest operation below). Data points further than pixels away are ignored. The default is 0.5i.
-height pixels
  Specifies the requested height of widget. The default is 4i.
-invertxy boolean
  Indicates whether the placement X-axis and Y-axis should be inverted. If boolean is true, the X and Y axes are swapped. The default is 0.
-justify justify
  Specifies how the title should be justified. This matters only when the title contains more than one line of text. Justify must be left, right, or center. The default is center.
-leftmargin pixels
  Sets the size of the margin from the left edge of the window to the Y-coordinate axis. If pixels is 0, the size is calculated automatically. The default is 0.
-plotbackground color
  Specifies the background color of the plotting area. The default is white.
-plotborderwidth pixels
  Sets the width of the 3-D border around the plotting area. The -plotrelief option determines if a border is drawn. The default is 2.
-plotpadx pad
  Sets the amount of padding to be added to the left and right sides of the plotting area. Pad can be a list of one or two screen distances. If pad has two elements, the left side of the plotting area entry is padded by the first distance and the right side by the second. If pad is just one distance, both the left and right sides are padded evenly. The default is 8.
-plotpady pad
  Sets the amount of padding to be added to the top and bottom of the plotting area. Pad can be a list of one or two screen distances. If pad has two elements, the top of the plotting area is padded by the first distance and the bottom by the second. If pad is just one distance, both the top and bottom are padded evenly. The default is 8.
-plotrelief relief
  Specifies the 3-D effect for the plotting area. Relief specifies how the interior of the plotting area should appear relative to rest of the graph; for example, raised means the plot should appear to protrude from the graph, relative to the surface of the graph. The default is sunken.
-relief relief
  Specifies the 3-D effect for the barchart widget. Relief specifies how the graph should appear relative to widget it is packed into; for example, raised means the graph should appear to protrude. The default is flat.
-rightmargin pixels
  Sets the size of margin from the plotting area to the right edge of the window. By default, the legend is drawn in this margin. If pixels is than 1, the margin size is selected automatically.
-takefocus focus
  Provides information used when moving the focus from window to window via keyboard traversal (e.g., Tab and Shift-Tab). If focus is 0, this means that this window should be skipped entirely during keyboard traversal. 1 means that the this window should always receive the input focus. An empty value means that the traversal scripts make the decision whether to focus on the window. The default is "".
-tile image
  Specifies a tiled background for the widget. If image isn't "", the background is tiled using image. Otherwise, the normal background color is drawn (see the -background option). Image must be an image created using the Tk image command. The default is "".
-title text
  Sets the title to text. If text is "", no title will be displayed.
-topmargin pixels
  Specifies the size of the margin above the x2 axis. If pixels is 0, the margin size is calculated automatically.
-width pixels
  Specifies the requested width of the widget. The default is 5i.

pathName crosshairs operation ?arg?
  See the CROSSHAIRS COMPONENT section.
pathName element operation ?arg?...
  See the ELEMENT COMPONENTS section.
pathName extents item
  Returns the size of a particular item in the graph. Item must be either leftmargin, rightmargin, topmargin, bottommargin, plotwidth, or plotheight.
pathName grid operation ?arg?...
  See the GRID COMPONENT section.
pathName invtransform winX winY
  Performs an inverse coordinate transformation, mapping window coordinates back to graph coordinates, using the standard X-axis and Y-axis. Returns a list of containing the X-Y graph coordinates.
pathName inside x y
  Returns 1 is the designated screen coordinate (x and y) is inside the plotting area and 0 otherwise.
pathName legend operation ?arg?...
  See the LEGEND COMPONENT section.
pathName line operation arg...
  The operation is the same as element.
pathName marker operation ?arg?...
  See the MARKER COMPONENTS section.
pathName metafile ?fileName?
  This operation is for Window platforms only. Creates a Windows enhanced metafile of the barchart. If present, fileName is the file name of the new metafile. Otherwise, the metafile is automatically added to the clipboard.
pathName postscript operation ?arg?...
  See the POSTSCRIPT COMPONENT section.
pathName snap photoName
  Takes a snapshot of the graph and stores the contents in the photo image photoName. PhotoName is the name of a Tk photo image that must already exist.
pathName transform x y
  Performs a coordinate transformation, mapping graph coordinates to window coordinates, using the standard X-axis and Y-axis. Returns a list containing the X-Y screen coordinates.
pathName xaxis operation ?arg?...
pathName x2axis operation ?arg?...
pathName yaxis operation ?arg?...
pathName y2axis operation ?arg?...
  See the AXIS COMPONENTS section.

## Barchart Components

A graph is composed of several components: coordinate axes, data elements, legend, grid, cross hairs, postscript, and annotation markers. Instead of one big set of configuration options and operations, the graph is partitioned, where each component has its own configuration options and operations that specifically control that aspect or part of the graph.

### Axis Components

Four coordinate axes are automatically created: two X-coordinate axes (x and x2) and two Y-coordinate axes (y, and y2). By default, the axis x is located in the bottom margin, y in the left margin, x2 in the top margin, and y2 in the right margin.

An axis consists of the axis line, title, major and minor ticks, and tick labels. Major ticks are drawn at uniform intervals along the axis. Each tick is labeled with its coordinate value. Minor ticks are drawn at uniform intervals within major ticks.

The range of the axis controls what region of data is plotted. Data points outside the minimum and maximum limits of the axis are not plotted. By default, the minimum and maximum limits are determined from the data, but you can reset either limit.

You can create and use several axes. To create an axis, invoke the axis component and its create operation.
`# Create a new axis called "temperature"
.b axis create temperature
`

You map data elements to an axis using the element's -mapy and -mapx configuration options. They specify the coordinate axes an element is mapped onto.
`# Now map the temperature data to this axis.
.b element create "temp" -xdata $x -ydata $tempData \
-mapy temperature
`

While you can have many axes, only four axes can be displayed simultaneously. They are drawn in each of the margins surrounding the plotting area. The axes x and y are drawn in the bottom and left margins. The axes x2 and y2 are drawn in top and right margins. Only x and y are shown by default. Note that the axes can have different scales.

To display a different axis, you invoke one of the following components: xaxis, yaxis, x2axis, and y2axis. The use operation designates the axis to be drawn in the corresponding margin: xaxis in the bottom, yaxis in the left, x2axis in the top, and y2axis in the right.
`# Display the axis temperature in the left margin.
.b yaxis use temperature
`

You can configure axes in many ways. The axis scale can be linear or logarithmic. The values along the axis can either monotonically increase or decrease. If you need custom tick labels, you can specify a Tcl procedure to format the label any way you wish. You can control how ticks are drawn, by changing the major tick interval or the number of minor ticks. You can define non-uniform tick intervals, such as for time-series plots.

pathName axis cget axisName option
  Returns the current value of the option given by option for axisName. Option may be any option described below for the axis configure operation.
pathName axis configure axisName ?axisName?... ?option value?...
  Queries or modifies the configuration options of axisName. Several axes can be changed. If option isn't specified, a list describing all the current options for axisName is returned. If option is specified, but not value, then a list describing option is returned. If one or more option and value pairs are specified, then for each pair, the axis option option is set to value. The following options are valid for axes.

-autorange range
  Sets the range of values for the axis to range. The axis limits are automatically reset to display the most recent data points in this range. If range is 0.0, the range is determined from the limits of the data. If -min or -max are specified, they override this option. The default is 0.0.
-color color
  Sets the color of the axis and tick labels. The default is black.
-command prefix
  Specifies a Tcl command to be invoked when formatting the axis tick labels. Prefix is a string containing the name of a Tcl proc and any extra arguments for the procedure. This command is invoked for each major tick on the axis. Two additional arguments are passed to the procedure: the pathname of the widget and the current the numeric value of the tick. The procedure returns the formatted tick label. If "" is returned, no label will appear next to the tick. You can get the standard tick labels again by setting prefix to "". The default is "".

  Please note that this procedure is invoked while the bar chart is redrawn. You may query the widget's configuration options. But do not reset options, because this can have unexpected results.

-descending boolean
  Indicates whether the values along the axis are monotonically increasing or decreasing. If boolean is true, the axis values will be decreasing. The default is 0.
-hide boolean
  Indicates whether the axis is displayed.
-justify justify
  Specifies how the axis title should be justified. This matters only when the axis title contains more than one line of text. Justify must be left, right, or center. The default is center.
-limits formatStr
  Specifies a printf-like description to format the minimum and maximum limits of the axis. The limits are displayed at the top/bottom or left/right sides of the plotting area. FormatStr is a list of one or two format descriptions. If one description is supplied, both the minimum and maximum limits are formatted in the same way. If two, the first designates the format for the minimum limit, the second for the maximum. If "" is given as either description, then the that limit will not be displayed. The default is "".
-linewidth pixels
  Sets the width of the axis and tick lines. The default is 1 pixel.
-logscale boolean
  Indicates whether the scale of the axis is logarithmic or linear. If boolean is true, the axis is logarithmic. The default scale is linear.
-loose boolean
  Indicates whether the limits of the axis should fit the data points tightly, at the outermost data points, or loosely, at the outer tick intervals. This is relevant only when the axis limit is automatically calculated. If boolean is true, the axis range is "loose". The default is 0.
-majorticks majorList
  Specifies where to display major axis ticks. You can use this option to display ticks at non-uniform intervals. MajorList is a list of axis coordinates designating the location of major ticks. No minor ticks are drawn. If majorList is "", major ticks will be automatically computed. The default is "".
-max value
  Sets the maximum limit of axisName. Any data point greater than value is not displayed. If value is "", the maximum limit is calculated using the largest data value. The default is "".
-min value
  Sets the minimum limit of axisName. Any data point less than value is not displayed. If value is "", the minimum limit is calculated using the smallest data value. The default is "".
-minorticks minorList
  Specifies where to display minor axis ticks. You can use this option to display minor ticks at non-uniform intervals. MinorList is a list of real values, ranging from 0.0 to 1.0, designating the placement of a minor tick. No minor ticks are drawn if the -majortick option is also set. If minorList is "", minor ticks will be automatically computed. The default is "".
-rotate theta
  Specifies the how many degrees to rotate the axis tick labels. Theta is a real value representing the number of degrees to rotate the tick labels. The default is 0.0 degrees.
-shiftby value
  Specifies how much to automatically shift the range of the axis. When the new data exceeds the current axis maximum, the maximum is increased in increments of value. You can use this option to prevent the axis limits from being recomputed at each new time point. If value is 0.0, then no automatic shifting is down. The default is 0.0.
-showticks boolean
  Indicates whether axis ticks should be drawn. If boolean is true, ticks are drawn. If false, only the axis line is drawn. The default is 1.
-stepsize value
  Specifies the interval between major axis ticks. If value isn't a valid interval (must be less than the axis range), the request is ignored and the step size is automatically calculated.
-subdivisions number
  Indicates how many minor axis ticks are to be drawn. For example, if number is two, only one minor tick is drawn. If number is one, no minor ticks are displayed. The default is 2.
-tickfont fontName
  Specifies the font for axis tick labels. The default is *-Courier-Bold-R-Normal-*-100-*.
-ticklength pixels
  Sets the length of major and minor ticks (minor ticks are half the length of major ticks). If pixels is less than zero, the axis will be inverted with ticks drawn pointing towards the plot. The default is 0.1i.
-title text
  Sets the title of the axis. If text is "", no axis title will be displayed.
-titlecolor color
  Sets the color of the axis title. The default is black.
-titlefont fontName
  Specifies the font for axis title. The default is *-Helvetica-Bold-R-Normal-*-14-140-*.

Axis configuration options may be also be set by the option command. The resource class is Axis. The resource names are the names of the axes (such as x or x2).
`option add *Barchart.Axis.Color blue
option add *Barchart.x.LogScale true
option add *Barchart.x2.LogScale false
`

pathName axis create axisName ?option value?...

  Creates a new axis by the name axisName. No axis by the same name can already exist. Option and value are described in above in the axis configure operation.
pathName axis delete ?axisName?...
  Deletes the named axes. An axis is not really deleted until it is not longer in use, so it's safe to delete axes mapped to elements.
pathName axis invtransform axisName value
  Performs the inverse transformation, changing the screen coordinate value to a graph coordinate, mapping the value mapped to axisName. Returns the graph coordinate.
pathName axis limits axisName
  Returns a list of the minimum and maximum limits for axisName. The order of the list is min max.
pathName axis names ?pattern?...
  Returns a list of axes matching zero or more patterns. If no pattern argument is give, the names of all axes are returned.
pathName axis transform axisName value
  Transforms the coordinate value to a screen coordinate by mapping the it to axisName. Returns the transformed screen coordinate.

Only four axes can be displayed simultaneously. By default, they are x, y, x2, and y2. You can swap in a different axis with use operation of the special axis components: xaxis, x2axis, yaxis, and y2axis.
`.g create axis temp
.g create axis time
...
.g xaxis use temp
.g yaxis use time
`

Only the axes specified for use are displayed on the screen.

The xaxis, x2axis, yaxis, and y2axis components operate on an axis location rather than a specific axis like the more general axis component does. The xaxis component manages the X-axis located in the bottom margin (whatever axis that happens to be). Likewise, yaxis uses the Y-axis in the left margin, x2axis the top X-axis, and y2axis the right Y-axis.

They implicitly control the axis that is currently using to that location. By default, xaxis uses the x axis, yaxis uses y, x2axis uses x2, and y2axis uses y2. These components can be more convenient to use than always determining what axes are current being displayed by the graph.

The following operations are available for axes. They mirror exactly the operations of the axis component. The axis argument must be xaxis, x2axis, yaxis, or y2axis.

pathName axis cget option
pathName axis configure ?option value?...
pathName axis invtransform value
pathName axis limits
pathName axis transform value
pathName axis use ?axisName?
  Designates the axis axisName is to be displayed at this location. AxisName can not be already in use at another location. This command returns the name of the axis currently using this location.

### Crosshairs Component

Cross hairs consist of two intersecting lines (one vertical and one horizontal) drawn completely across the plotting area. They are used to position the mouse in relation to the coordinate axes. Cross hairs differ from line markers in that they are implemented using XOR drawing primitives. This means that they can be quickly drawn and erased without redrawing the entire widget.

The following operations are available for cross hairs:

pathName crosshairs cget option
  Returns the current value of the cross hairs configuration option given by option. Option may be any option described below for the cross hairs configure operation.
pathName crosshairs configure ?option value?...
  Queries or modifies the configuration options of the cross hairs. If option isn't specified, a list describing all the current options for the cross hairs is returned. If option is specified, but not value, then a list describing option is returned. If one or more option and value pairs are specified, then for each pair, the cross hairs option option is set to value. The following options are available for cross hairs.

-color color
  Sets the color of the cross hairs. The default is black.
-dashes dashList
  Sets the dash style of the cross hairs. DashList is a list of up to 11 numbers that alternately represent the lengths of the dashes and gaps on the cross hair lines. Each number must be between 1 and 255. If dashList is "", the cross hairs will be solid lines.
-hide boolean
  Indicates whether cross hairs are drawn. If boolean is true, cross hairs are not drawn. The default is yes.
-linewidth pixels
  Set the width of the cross hair lines. The default is 1.
-position pos
  Specifies the screen position where the cross hairs intersect. Pos must be in the form "@x,y", where x and y are the window coordinates of the intersection.

Cross hairs configuration options may be also be set by the option command. The resource name and class are crosshairs and Crosshairs respectively.
`option add *Barchart.Crosshairs.LineWidth 2
option add *Barchart.Crosshairs.Color red
`

pathName crosshairs off

  Turns off the cross hairs.
pathName crosshairs on
  Turns on the display of the cross hairs.
pathName crosshairs toggle
  Toggles the current state of the cross hairs, alternately mapping and unmapping the cross hairs.

## Elements

A data element represents a set of data. It contains x and y vectors which are the coordinates of the data points. Elements are displayed as bars where the length of the bar is proportional to the ordinate of the data point. Elements also control the appearance of the data, such as the color, stipple, relief, etc.

When new data elements are created, they are automatically added to a list of displayed elements. The display list controls what elements are drawn and in what order.

The following operations are available for elements.

pathName element activate elemName ?index?...
  Specifies the data points of element elemName to be drawn using active foreground and background colors. ElemName is the name of the element and index is a number representing the index of the data point. If no indices are present then all data points become active.
pathName element bind tagName ?sequence? ?command?
  Associates command with tagName such that whenever the event sequence given by sequence occurs for an element with this tag, command will be invoked. The syntax is similar to the bind command except that it operates on graph elements, rather than widgets. See the bind manual entry for complete details on sequence and the substitutions performed on command before invoking it.

  If all arguments are specified then a new binding is created, replacing any existing binding for the same sequence and tagName. If the first character of command is + then command augments an existing binding rather than replacing it. If no command argument is provided then the command currently associated with tagName and sequence (it's an error occurs if there's no such binding) is returned. If both command and sequence are missing then a list of all the event sequences for which bindings have been defined for tagName.

pathName element cget elemName option
  Returns the current value of the element configuration option given by option. Option may be any of the options described below for the element configure operation.
pathName element closest x y ?option value?... ?elemName?...
  Finds the data point representing the bar closest to the window coordinates x and y in the element elemName. ElemName is the name of an element, which must be displayed. If no elements are specified, then all displayed elements are searched. It returns a list containing the name of the closest element, the index of its closest point, and the graph coordinates of the point. If no data point within the threshold distance can be found, "" is returned. The following option-value pairs are available.

-halo pixels
  Specifies a threshold distance where selected data points are ignored. Pixels is a valid screen distance, such as 2 or 1.2i. If this option isn't specified, then it defaults to the value of the barchart's -halo option.

pathName element configure elemName ?elemName... ?option value?...
  Queries or modifies the configuration options for elements. Several elements can be modified at the same time. If option isn't specified, a list describing all the current options for elemName is returned. If option is specified, but not value, then a list describing the option option is returned. If one or more option and value pairs are specified, then for each pair, the element option option is set to value. The following options are valid for elements.

-activepen penName
  Specifies pen to use to draw active element. If penName is "", no active elements will be drawn. The default is activeLine.
-bindtags tagList
  Specifies the binding tags for the element. TagList is a list of binding tag names. The tags and their order will determine how events for elements. Each tag in the list matching the current event sequence will have its Tcl command executed. Implicitly the name of the element is always the first tag in the list. The default value is all.
-background color
  Sets the the color of the border around each bar. The default is white.
-barwidth value
  Specifies the width the bars drawn for the element. Value is the width in X-coordinates. If this option isn't specified, the width of each bar is the value of the widget's -barwidth option.
-baseline value
  Specifies the baseline of the bar segments. This affects how bars are drawn since bars are drawn from their respective y-coordinate the baseline. By default the baseline is 0.0.
-borderwidth pixels
  Sets the border width of the 3-D border drawn around the outside of each bar. The -relief option determines if such a border is drawn. Pixels must be a valid screen distance like 2 or 0.25i. The default is 2.
-data coordList
  Specifies the X-Y coordinates of the data. CoordList is a list of numeric expressions representing the X-Y coordinate pairs of each data point.
-foreground color
  Sets the color of the interior of the bars.
-hide boolean
  Indicates whether the element is displayed. The default is no.
-label text
  Sets the element's label in the legend. If text is "", the element will have no entry in the legend. The default label is the element's name.
-mapx xAxis
  Selects the X-axis to map the element's X-coordinates onto. XAxis must be the name of an axis. The default is x.
-mapy yAxis
  Selects the Y-axis to map the element's Y-coordinates onto. YAxis must be the name of an axis. The default is y.
-relief string
  Specifies the 3-D effect desired for bars. Relief indicates how the interior of the bar should appear relative to the surface of the chart; for example, raised means the bar should appear to protrude from the surface of the plotting area. The default is raised.
-stipple bitmap
  Specifies a stipple pattern with which to draw the bars. If bitmap is "", then the bar is drawn in a solid fashion.
-xdata xVector
  Specifies the x-coordinate vector of the data. XVector is the name of a BLT vector or a list of numeric expressions.
-ydata yVector
  Specifies the y-coordinate vector of the data. YVector is the name of a BLT vector or a list of numeric expressions.

Element configuration options may also be set by the option command. The resource names in the option database are prefixed by elem.
`option add *Barchart.Element.background blue
`

pathName element create elemName ?option value?...

  Creates a new element elemName. Element names must be unique, so an element elemName may not already exist. If additional arguments are present, they specify any of the element options valid for element configure operation.
pathName element deactivate pattern...
  Deactivates all the elements matching pattern for the graph. Elements whose names match any of the patterns given are redrawn using their normal colors.
pathName element delete ?pattern?...
  Deletes all the elements matching pattern for the graph. Elements whose names match any of the patterns given are deleted. The graph will be redrawn without the deleted elements.
pathName element exists elemName
  Returns 1 if an element elemName currently exists and 0 otherwise.
pathName element names ?pattern?...
  Returns the elements matching one or more pattern. If no pattern is given, the names of all elements is returned.
pathName element show ?nameList?
  Queries or modifies the element display list. The element display list designates the elements drawn and in what order. NameList is a list of elements to be displayed in the order they are named. If there is no nameList argument, the current display list is returned.
pathName element type elemName
  Returns the type of elemName. If the element is a bar element, the commands returns the string "bar", otherwise it returns "line".

###

Grid Component

Grid lines extend from the major and minor ticks of each axis horizontally or vertically across the plotting area. The following operations are available for grid lines.

pathName grid cget option
  Returns the current value of the grid line configuration option given by option. Option may be any option described below for the grid configure operation.
pathName grid configure ?option value?...
  Queries or modifies the configuration options for grid lines. If option isn't specified, a list describing all the current grid options for pathName is returned. If option is specified, but not value, then a list describing option is returned. If one or more option and value pairs are specified, then for each pair, the grid line option option is set to value. The following options are valid for grid lines.

-color color
  Sets the color of the grid lines. The default is black.
-dashes dashList
  Sets the dash style of the grid lines. DashList is a list of up to 11 numbers that alternately represent the lengths of the dashes and gaps on the grid lines. Each number must be between 1 and 255. If dashList is "", the grid will be solid lines.
-hide boolean
  Indicates whether the grid should be drawn. If boolean is true, grid lines are not shown. The default is yes.
-linewidth pixels
  Sets the width of grid lines. The default width is 1.
-mapx xAxis
  Specifies the X-axis to display grid lines. XAxis must be the name of an axis or "" for no grid lines. The default is "".
-mapy yAxis
  Specifies the Y-axis to display grid lines. YAxis must be the name of an axis or "" for no grid lines. The default is y.
-minor boolean
  Indicates whether the grid lines should be drawn for minor ticks. If boolean is true, the lines will appear at minor tick intervals. The default is 1.

Grid configuration options may also be set by the option command. The resource name and class are grid and Grid respectively.
`option add *Barchart.grid.LineWidth 2
option add *Barchart.Grid.Color black
`

pathName grid off

  Turns off the display the grid lines.
pathName grid on
  Turns on the display the grid lines.
pathName grid toggle
  Toggles the display of the grid.

### Legend Component

The legend displays a list of the data elements. Each entry consists of the element's symbol and label. The legend can appear in any margin (the default location is in the right margin). It can also be positioned anywhere within the plotting area.

The following operations are valid for the legend.

pathName legend activate pattern...
  Selects legend entries to be drawn using the active legend colors and relief. All entries whose element names match pattern are selected. To be selected, the element name must match only one pattern.
pathName legend bind tagName ?sequence? ?command?
  Associates command with tagName such that whenever the event sequence given by sequence occurs for a legend entry with this tag, command will be invoked. Implicitly the element names in the entry are tags. The syntax is similar to the bind command except that it operates on legend entries, rather than widgets. See the bind manual entry for complete details on sequence and the substitutions performed on command before invoking it.

  If all arguments are specified then a new binding is created, replacing any existing binding for the same sequence and tagName. If the first character of command is + then command augments an existing binding rather than replacing it. If no command argument is provided then the command currently associated with tagName and sequence (it's an error occurs if there's no such binding) is returned. If both command and sequence are missing then a list of all the event sequences for which bindings have been defined for tagName.

pathName legend cget option
  Returns the current value of a legend configuration option. Option may be any option described below in the legend configure operation.
pathName legend configure ?option value?...
  Queries or modifies the configuration options for the legend. If option isn't specified, a list describing the current legend options for pathName is returned. If option is specified, but not value, then a list describing option is returned. If one or more option and value pairs are specified, then for each pair, the legend option option is set to value. The following options are valid for the legend.

-activebackground color
  Sets the background color for active legend entries. All legend entries marked active (see the legend activate operation) are drawn using this background color.
-activeborderwidth pixels
  Sets the width of the 3-D border around the outside edge of the active legend entries. The default is 2.
-activeforeground color
  Sets the foreground color for active legend entries. All legend entries marked as active (see the legend activate operation) are drawn using this foreground color.
-activerelief relief
  Specifies the 3-D effect desired for active legend entries. Relief denotes how the interior of the entry should appear relative to the legend; for example, raised means the entry should appear to protrude from the legend, relative to the surface of the legend. The default is flat.
-anchor anchor
  Tells how to position the legend relative to the positioning point for the legend. This is dependent on the value of the -position option. The default is center.

left or right
  The anchor describes how to position the legend vertically.
top or bottom
  The anchor describes how to position the legend horizontally.
@x,y
  The anchor specifies how to position the legend relative to the positioning point. For example, if anchor is center then the legend is centered on the point; if anchor is n then the legend will be drawn such that the top center point of the rectangular region occupied by the legend will be at the positioning point.
plotarea
  The anchor specifies how to position the legend relative to the plotting area. For example, if anchor is center then the legend is centered in the plotting area; if anchor is ne then the legend will be drawn such that occupies the upper right corner of the plotting area.

-background color
  Sets the background color of the legend. If color is "", the legend background with be transparent.
-bindtags tagList
  Specifies the binding tags for legend entries. TagList is a list of binding tag names. The tags and their order will determine how events for legend entries. Each tag in the list matching the current event sequence will have its Tcl command executed. The default value is all.
-borderwidth pixels
  Sets the width of the 3-D border around the outside edge of the legend (if such border is being drawn; the relief option determines this). The default is 2 pixels.
-font fontName
  FontName specifies a font to use when drawing the labels of each element into the legend. The default is *-Helvetica-Bold-R-Normal-*-12-120-*.
-foreground color
  Sets the foreground color of the text drawn for the element's label. The default is black.
-hide boolean
  Indicates whether the legend should be displayed. If boolean is true, the legend will not be draw. The default is no.
-ipadx pad
  Sets the amount of internal padding to be added to the width of each legend entry. Pad can be a list of one or two screen distances. If pad has two elements, the left side of the legend entry is padded by the first distance and the right side by the second. If pad is just one distance, both the left and right sides are padded evenly. The default is 2.
-ipady pad
  Sets an amount of internal padding to be added to the height of each legend entry. Pad can be a list of one or two screen distances. If pad has two elements, the top of the entry is padded by the first distance and the bottom by the second. If pad is just one distance, both the top and bottom of the entry are padded evenly. The default is 2.
-padx pad
  Sets the padding to the left and right exteriors of the legend. Pad can be a list of one or two screen distances. If pad has two elements, the left side of the legend is padded by the first distance and the right side by the second. If pad has just one distance, both the left and right sides are padded evenly. The default is 4.
-pady pad
  Sets the padding above and below the legend. Pad can be a list of one or two screen distances. If pad has two elements, the area above the legend is padded by the first distance and the area below by the second. If pad is just one distance, both the top and bottom areas are padded evenly. The default is 0.
-position pos
  Specifies where the legend is drawn. The -anchor option also affects where the legend is positioned. If pos is left, left, top, or bottom, the legend is drawn in the specified margin. If pos is plotarea, then the legend is drawn inside the plotting area at a particular anchor. If pos is in the form "@x,y", where x and y are the window coordinates, the legend is drawn in the plotting area at the specified coordinates. The default is right.
-raised boolean
  Indicates whether the legend is above or below the data elements. This matters only if the legend is in the plotting area. If boolean is true, the legend will be drawn on top of any elements that may overlap it. The default is no.
-relief relief
  Specifies the 3-D effect for the border around the legend. Relief specifies how the interior of the legend should appear relative to the bar chart; for example, raised means the legend should appear to protrude from the bar chart, relative to the surface of the bar chart. The default is sunken.

Legend configuration options may also be set by the option command. The resource name and class are legend and Legend respectively.
`option add *Barchart.legend.Foreground blue
option add *Barchart.Legend.Relief raised
`

pathName legend deactivate pattern...

  Selects legend entries to be drawn using the normal legend colors and relief. All entries whose element names match pattern are selected. To be selected, the element name must match only one pattern.
pathName legend get pos
  Returns the name of the element whose entry is at the screen position pos in the legend. Pos must be in the form "@x,y", where x and y are window coordinates. If the given coordinates do not lie over a legend entry, "" is returned.

### Pen Components

Pens define attributes for elements. Pens mirror the configuration options of data elements that pertain to how symbols and lines are drawn. Data elements use pens to determine how they are drawn. A data element may use several pens at once. In this case, the pen used for a particular data point is determined from each element's weight vector (see the element's -weight and -style options).

One pen, called activeBar, is automatically created. It's used as the default active pen for elements. So you can change the active attributes for all elements by simply reconfiguring this pen.
`.g pen configure "activeBar" -fg green -bg green4
`

You can create and use several pens. To create a pen, invoke the pen component and its create operation.
`.g pen create myPen
`

You map pens to a data element using either the element's -pen or -activepen options.
`.g element create "e1" -xdata $x -ydata $tempData \
-pen myPen
`

An element can use several pens at once. This is done by specifying the name of the pen in the element's style list (see the -styles option).
`.g element configure "e1" -styles { myPen 2.0 3.0 }
`

This says that any data point with a weight between 2.0 and 3.0 is to be drawn using the pen myPen. All other points are drawn with the element's default attributes.

The following operations are available for pen components.

pathName pen cget penName option
  Returns the current value of the option given by option for penName. Option may be any option described below for the pen configure operation.
pathName pen configure penName ?penName... ?option value?...
  Queries or modifies the configuration options of penName. Several pens can be modified at once. If option isn't specified, a list describing the current options for penName is returned. If option is specified, but not value, then a list describing option is returned. If one or more option and value pairs are specified, then for each pair, the pen option option is set to value. The following options are valid for pens.

-background color
  Sets the the color of the border around each bar. The default is white.
-borderwidth pixels
  Sets the border width of the 3-D border drawn around the outside of each bar. The -relief option determines if such a border is drawn. Pixels must be a valid screen distance like 2 or 0.25i. The default is 2.
-foreground color
  Sets the color of the interior of the bars.
-relief string
  Specifies the 3-D effect desired for bars. Relief indicates how the interior of the bar should appear relative to the surface of the chart; for example, raised means the bar should appear to protrude from the bar chart, relative to the surface of the plotting area. The default is raised.
-stipple bitmap
  Specifies a stipple pattern with which to draw the bars. If bitmap is "", then the bar is drawn in a solid fashion.
-type elemType
  Specifies the type of element the pen is to be used with. This option should only be employed when creating the pen. This is for those that wish to mix different types of elements (bars and lines) on the same graph. The default type is "bar".

Pen configuration options may be also be set by the option command. The resource class is Pen. The resource names are the names of the pens.
`option add *Barchart.Pen.Foreground`` `` blue
option add *Barchart.activeBar.foreground green
`

pathName pen create penName ?option value?...

  Creates a new pen by the name penName. No pen by the same name can already exist. Option and value are described in above in the pen configure operation.
pathName pen delete ?penName?...
  Deletes the named pens. A pen is not really deleted until it is not longer in use, so it's safe to delete pens mapped to elements.
pathName pen names ?pattern?...
  Returns a list of pens matching zero or more patterns. If no pattern argument is give, the names of all pens are returned.

### PostScript Component

The barchart can generate encapsulated PostScript output. There are several configuration options you can specify to control how the plot will be generated. You can change the page dimensions and borders. The plot itself can be scaled, centered, or rotated to landscape. The PostScript output can be written directly to a file or returned through the interpreter.

The following postscript operations are available.

pathName postscript cget option
  Returns the current value of the postscript option given by option. Option may be any option described below for the postscript configure operation.
pathName postscript configure ?option value?...
  Queries or modifies the configuration options for PostScript generation. If option isn't specified, a list describing the current postscript options for pathName is returned. If option is specified, but not value, then a list describing option is returned. If one or more option and value pairs are specified, then for each pair, the postscript option option is set to value. The following postscript options are available.

-center boolean
  Indicates whether the plot should be centered on the PostScript page. If boolean is false, the plot will be placed in the upper left corner of the page. The default is 1.
-colormap varName
  VarName must be the name of a global array variable that specifies a color mapping from the X color name to PostScript. Each element of varName must consist of PostScript code to set a particular color value (e.g. ``1.0 1.0 0.0 setrgbcolor''). When generating color information in PostScript, the array variable varName is checked if an element of the name as the color exists. If so, it uses its value as the PostScript command to set the color. If this option hasn't been specified, or if there isn't an entry in varName for a given color, then it uses the red, green, and blue intensities from the X color.
-colormode mode
  Specifies how to output color information. Mode must be either color (for full color output), gray (convert all colors to their gray-scale equivalents) or mono (convert foreground colors to black and background colors to white). The default mode is color.
-fontmap varName
  VarName must be the name of a global array variable that specifies a font mapping from the X font name to PostScript. Each element of varName must consist of a Tcl list with one or two elements; the name and point size of a PostScript font. When outputting PostScript commands for a particular font, the array variable varName is checked to see if an element by the specified font exists. If there is such an element, then the font information contained in that element is used in the PostScript output. (If the point size is omitted from the list, the point size of the X font is used). Otherwise the X font is examined in an attempt to guess what PostScript font to use. This works only for fonts whose foundry property is Adobe (such as Times, Helvetica, Courier, etc.). If all of this fails then the font defaults to Helvetica-Bold.
-decorations boolean
  Indicates whether PostScript commands to generate color backgrounds and 3-D borders will be output. If boolean is false, the graph will background will be white and no 3-D borders will be generated. The default is 1.
-height pixels
  Sets the height of the plot. This lets you print the bar chart with a height different from the one drawn on the screen. If pixels is 0, the height is the same as the widget's height. The default is 0.
-landscape boolean
  If boolean is true, this specifies the printed area is to be rotated 90 degrees. In non-rotated output the X-axis of the printed area runs along the short dimension of the page (``portrait'' orientation); in rotated output the X-axis runs along the long dimension of the page (``landscape'' orientation). Defaults to 0.
-maxpect boolean
  Indicates to scale the plot so that it fills the PostScript page. The aspect ratio of the barchart is still retained. The default is 0.
-padx pad
  Sets the horizontal padding for the left and right page borders. The borders are exterior to the plot. Pad can be a list of one or two screen distances. If pad has two elements, the left border is padded by the first distance and the right border by the second. If pad has just one distance, both the left and right borders are padded evenly. The default is 1i.
-pady pad
  Sets the vertical padding for the top and bottom page borders. The borders are exterior to the plot. Pad can be a list of one or two screen distances. If pad has two elements, the top border is padded by the first distance and the bottom border by the second. If pad has just one distance, both the top and bottom borders are padded evenly. The default is 1i.
-paperheight pixels
  Sets the height of the postscript page. This can be used to select between different page sizes (letter, A4, etc). The default height is 11.0i.
-paperwidth pixels
  Sets the width of the postscript page. This can be used to select between different page sizes (letter, A4, etc). The default width is 8.5i.
-width pixels
  Sets the width of the plot. This lets you generate a plot of a width different from that of the widget. If pixels is 0, the width is the same as the widget's width. The default is 0.

Postscript configuration options may be also be set by the option command. The resource name and class are postscript and Postscript respectively.
`option add *Barchart.postscript.Decorations false
option add *Barchart.Postscript.Landscape true
`

pathName postscript output ?fileName? ?option value?...

  Outputs a file of encapsulated PostScript. If a fileName argument isn't present, the command returns the PostScript. If any option-value pairs are present, they set configuration options controlling how the PostScript is generated. Option and value can be anything accepted by the postscript configure operation above.

### Marker Components

Markers are simple drawing procedures used to annotate or highlight areas of the graph. Markers have various types: text strings, bitmaps, images, connected lines, windows, or polygons. They can be associated with a particular element, so that when the element is hidden or un-hidden, so is the marker. By default, markers are the last items drawn, so that data elements will appear in behind them. You can change this by configuring the -under option.

Markers, in contrast to elements, don't affect the scaling of the coordinate axes. They can also have elastic coordinates (specified by -Inf and Inf respectively) that translate into the minimum or maximum limit of the axis. For example, you can place a marker so it always remains in the lower left corner of the plotting area, by using the coordinates -Inf,-Inf.

The following operations are available for markers.

pathName marker after markerId ?afterId?
  Changes the order of the markers, drawing the first marker after the second. If no second afterId argument is specified, the marker is placed at the end of the display list. This command can be used to control how markers are displayed since markers are drawn in the order of this display list.
pathName marker before markerId ?beforeId?
  Changes the order of the markers, drawing the first marker before the second. If no second beforeId argument is specified, the marker is placed at the beginning of the display list. This command can be used to control how markers are displayed since markers are drawn in the order of this display list.
pathName marker bind tagName ?sequence? ?command?
  Associates command with tagName such that whenever the event sequence given by sequence occurs for a marker with this tag, command will be invoked. The syntax is similar to the bind command except that it operates on graph markers, rather than widgets. See the bind manual entry for complete details on sequence and the substitutions performed on command before invoking it.

  If all arguments are specified then a new binding is created, replacing any existing binding for the same sequence and tagName. If the first character of command is + then command augments an existing binding rather than replacing it. If no command argument is provided then the command currently associated with tagName and sequence (it's an error occurs if there's no such binding) is returned. If both command and sequence are missing then a list of all the event sequences for which bindings have been defined for tagName.

pathName marker cget option
  Returns the current value of the marker configuration option given by option. Option may be any option described below in the configure operation.
pathName marker configure markerId ?option value?...
  Queries or modifies the configuration options for markers. If option isn't specified, a list describing the current options for markerId is returned. If option is specified, but not value, then a list describing option is returned. If one or more option and value pairs are specified, then for each pair, the marker option option is set to value.

  The following options are valid for all markers. Each type of marker also has its own type-specific options. They are described in the sections below.

-bindtags tagList
  Specifies the binding tags for the marker. TagList is a list of binding tag names. The tags and their order will determine how events for markers are handled. Each tag in the list matching the current event sequence will have its Tcl command executed. Implicitly the name of the marker is always the first tag in the list. The default value is all.
-coords coordList
  Specifies the coordinates of the marker. CoordList is a list of graph coordinates. The number of coordinates required is dependent on the type of marker. Text, image, and window markers need only two coordinates (an X-Y coordinate). Bitmap markers can take either two or four coordinates (if four, they represent the corners of the bitmap). Line markers need at least four coordinates, polygons at least six. If coordList is "", the marker will not be displayed. The default is "".
-element elemName
  Links the marker with the element elemName. The marker is drawn only if the element is also currently displayed (see the element's show operation). If elemName is "", the marker is always drawn. The default is "".
-hide boolean
  Indicates whether the marker is drawn. If boolean is true, the marker is not drawn. The default is no.
-mapx xAxis
  Specifies the X-axis to map the marker's X-coordinates onto. XAxis must the name of an axis. The default is x.
-mapy yAxis
  Specifies the Y-axis to map the marker's Y-coordinates onto. YAxis must the name of an axis. The default is y.
-name markerId
  Changes the identifier for the marker. The identifier markerId can not already be used by another marker. If this option isn't specified, the marker's name is uniquely generated.
-under boolean
  Indicates whether the marker is drawn below/above data elements. If boolean is true, the marker is be drawn underneath the data elements. Otherwise, the marker is drawn on top of the element. The default is 0.
-xoffset pixels
  Specifies a screen distance to offset the marker horizontally. Pixels is a valid screen distance, such as 2 or 1.2i. The default is 0.
-yoffset pixels
  Specifies a screen distance to offset the markers vertically. Pixels is a valid screen distance, such as 2 or 1.2i. The default is 0.

Marker configuration options may also be set by the option command. The resource class is either BitmapMarker, ImageMarker, LineMarker, PolygonMarker, TextMarker, or WindowMarker, depending on the type of marker. The resource name is the name of the marker.
`option add *Barchart.TextMarker.Foreground white
option add *Barchart.BitmapMarker.Foreground white
option add *Barchart.m1.Background blue
`

pathName marker create type ?option value?...

  Creates a marker of the selected type. Type may be either text, line, bitmap, image, polygon, or window. This command returns the marker identifier, used as the markerId argument in the other marker-related commands. If the -name option is used, this overrides the normal marker identifier. If the name provided is already used for another marker, the new marker will replace the old.
pathName marker delete ?name?...
  Removes one of more markers. The graph will automatically be redrawn without the marker..
pathName marker exists markerId
  Returns 1 if the marker markerId exists and 0 otherwise.
pathName marker names ?pattern?
  Returns the names of all the markers that currently exist. If pattern is supplied, only those markers whose names match it will be returned.
pathName marker type markerId
  Returns the type of the marker given by markerId, such as line or text. If markerId is not a valid a marker identifier, "" is returned.

### Bitmap Markers

A bitmap marker displays a bitmap. The size of the bitmap is controlled by the number of coordinates specified. If two coordinates, they specify the position of the top-left corner of the bitmap. The bitmap retains its normal width and height. If four coordinates, the first and second pairs of coordinates represent the corners of the bitmap. The bitmap will be stretched or reduced as necessary to fit into the bounding rectangle.

Bitmap markers are created with the marker's create operation in the form:

`pathName marker create bitmap ?option value?...
`

There may be many option-value pairs, each sets a configuration options for the marker. These same option-value pairs may be used with the marker's configure operation.

The following options are specific to bitmap markers:

-background color
  Same as the -fill option.
-bitmap bitmap
  Specifies the bitmap to be displayed. If bitmap is "", the marker will not be displayed. The default is "".
-fill color
  Sets the background color of the bitmap. If color is the empty string, no background will be transparent. The default background color is "".
-foreground color
  Same as the -outline option.
-mask mask
  Specifies a mask for the bitmap to be displayed. This mask is a bitmap itself, denoting the pixels that are transparent. If mask is "", all pixels of the bitmap will be drawn. The default is "".
-outline color
  Sets the foreground color of the bitmap. The default value is black.
-rotate theta
  Sets the rotation of the bitmap. Theta is a real number representing the angle of rotation in degrees. The marker is first rotated and then placed according to its anchor position. The default rotation is 0.0.

### Image Markers

A image marker displays an image. Image markers are created with the marker's create operation in the form:

`pathName marker create image ?option value?...
`

There may be many option-value pairs, each sets a configuration option for the marker. These same option-value pairs may be used with the marker's configure operation.

The following options are specific to image markers:

-anchor anchor
  Anchor tells how to position the image relative to the positioning point for the image. For example, if anchor is center then the image is centered on the point; if anchor is n then the image will be drawn such that the top center point of the rectangular region occupied by the image will be at the positioning point. This option defaults to center.
-image image
  Specifies the image to be drawn. If image is "", the marker will not be drawn. The default is "".

### Line Markers

A line marker displays one or more connected line segments. Line markers are created with marker's create operation in the form:

`pathName marker create line ?option value?...
`

There may be many option-value pairs, each sets a configuration option for the marker. These same option-value pairs may be used with the marker's configure operation.

The following options are specific to line markers:

-dashes dashList
  Sets the dash style of the line. DashList is a list of up to 11 numbers that alternately represent the lengths of the dashes and gaps on the line. Each number must be between 1 and 255. If dashList is "", the marker line will be solid.
-fill color
  Sets the background color of the line. This color is used with striped lines (see the -fdashesR option). If color is the empty string, no background color is drawn (the line will be dashed, not striped). The default background color is "".
-linewidth pixels
  Sets the width of the lines. The default width is 0.
-outline color
  Sets the foreground color of the line. The default value is black.
-stipple bitmap
  Specifies a stipple pattern used to draw the line, rather than a solid line. Bitmap specifies a bitmap to use as the stipple pattern. If bitmap is "", then the line is drawn in a solid fashion. The default is "".

### Polygon Markers

A polygon marker displays a closed region described as two or more connected line segments. It is assumed the first and last points are connected. Polygon markers are created using the marker create operation in the form:

`pathName marker create polygon ?option value?...
`

There may be many option-value pairs, each sets a configuration option for the marker. These same option-value pairs may be used with the marker configure command to change the marker's configuration. The following options are supported for polygon markers:

-dashes dashList
  Sets the dash style of the outline of the polygon. DashList is a list of up to 11 numbers that alternately represent the lengths of the dashes and gaps on the outline. Each number must be between 1 and 255. If dashList is "", the outline will be a solid line.
-fill color
  Sets the fill color of the polygon. If color is "", then the interior of the polygon is transparent. The default is white.
-linewidth pixels
  Sets the width of the outline of the polygon. If pixels is zero, no outline is drawn. The default is 0.
-outline color
  Sets the color of the outline of the polygon. If the polygon is stippled (see the -stipple option), then this represents the foreground color of the stipple. The default is black.
-stipple bitmap
  Specifies that the polygon should be drawn with a stippled pattern rather than a solid color. Bitmap specifies a bitmap to use as the stipple pattern. If bitmap is "", then the polygon is filled with a solid color (if the -fill option is set). The default is "".

### Text Markers

A text marker displays a string of characters on one or more lines of text. Embedded newlines cause line breaks. They may be used to annotate regions of the graph. Text markers are created with the create operation in the form:

`pathName marker create text ?option value?...
`

There may be many option-value pairs, each sets a configuration option for the text marker. These same option-value pairs may be used with the marker's configure operation.

The following options are specific to text markers:

-anchor anchor
  Anchor tells how to position the text relative to the positioning point for the text. For example, if anchor is center then the text is centered on the point; if anchor is n then the text will be drawn such that the top center point of the rectangular region occupied by the text will be at the positioning point. This default is center.
-background color
  Same as the -fill option.
-font fontName
  Specifies the font of the text. The default is *-Helvetica-Bold-R-Normal-*-120-*.
-fill color
  Sets the background color of the text. If color is the empty string, no background will be transparent. The default background color is "".
-foreground color
  Same as the -outline option.
-justify justify
  Specifies how the text should be justified. This matters only when the marker contains more than one line of text. Justify must be left, right, or center. The default is center.
-outline color
  Sets the color of the text. The default value is black.
-padx pad
  Sets the padding to the left and right exteriors of the text. Pad can be a list of one or two screen distances. If pad has two elements, the left side of the text is padded by the first distance and the right side by the second. If pad has just one distance, both the left and right sides are padded evenly. The default is 4.
-pady pad
  Sets the padding above and below the text. Pad can be a list of one or two screen distances. If pad has two elements, the area above the text is padded by the first distance and the area below by the second. If pad is just one distance, both the top and bottom areas are padded evenly. The default is 4.
-rotate theta
  Specifies the number of degrees to rotate the text. Theta is a real number representing the angle of rotation. The marker is first rotated along its center and is then drawn according to its anchor position. The default is 0.0.
-text text
  Specifies the text of the marker. The exact way the text is displayed may be affected by other options such as -anchor or -rotate.

### Window Markers

A window marker displays a widget at a given position. Window markers are created with the marker's create operation in the form:

`pathName marker create window ?option value?...
`

There may be many option-value pairs, each sets a configuration option for the marker. These same option-value pairs may be used with the marker's configure command.

The following options are specific to window markers:

-anchor anchor
  Anchor tells how to position the widget relative to the positioning point for the widget. For example, if anchor is center then the widget is centered on the point; if anchor is n then the widget will be displayed such that the top center point of the rectangular region occupied by the widget will be at the positioning point. This option defaults to center.
-height pixels
  Specifies the height to assign to the marker's window. If this option isn't specified, or if it is specified as "", then the window is given whatever height the widget requests internally.
-width pixels
  Specifies the width to assign to the marker's window. If this option isn't specified, or if it is specified as "", then the window is given whatever width the widget requests internally.
-window pathName
  Specifies the widget to be managed by the barchart. PathName must be a child of the barchart widget.

## Graph Component Bindings

Specific barchart components, such as elements, markers and legend entries, can have a command trigger when event occurs in them, much like canvas items in Tk's canvas widget. Not all event sequences are valid. The only binding events that may be specified are those related to the mouse and keyboard (such as Enter, Leave, ButtonPress, Motion, and KeyPress).

Only one element or marker can be picked during an event. This means, that if the mouse is directly over both an element and a marker, only the uppermost component is selected. This isn't true for legend entries. Both a legend entry and an element (or marker) binding commands will be invoked if both items are picked.

It is possible for multiple bindings to match a particular event. This could occur, for example, if one binding is associated with the element name and another is associated with one of the element's tags (see the -bindtags option). When this occurs, all of the matching bindings are invoked. A binding associated with the element name is invoked first, followed by one binding for each of the element's bindtags. If there are multiple matching bindings for a single tag, then only the most specific binding is invoked. A continue command in a binding script terminates that script, and a break command terminates that script and skips any remaining scripts for the event, just as for the bind command.

The -bindtags option for these components controls addition tag names which can be matched. Implicitly elements and markers always have tags matching their names. Setting the value of the -bindtags option doesn't change this.

## C Language API

You can manipulate data elements from the C language. There may be situations where it is too expensive to translate the data values from ASCII strings. Or you might want to read data in a special file format.

Data can manipulated from the C language using BLT vectors. You specify the X-Y data coordinates of an element as vectors and manipulate the vector from C. The barchart will be redrawn automatically after the vectors are updated.

From Tcl, create the vectors and configure the element to use them.
`vector X Y
.g element configure line1 -xdata X -ydata Y
`

To set data points from C, you pass the values as arrays of doubles using the Blt_ResetVector call. The vector is reset with the new data and at the next idle point (when Tk re-enters its event loop), the graph will be redrawn automatically.
`#include <tcl.h>
#include <blt.h>
`

register int i;
Blt_Vector *xVec, *yVec;
double x[50], y[50];

/* Get the BLT vectors "X" and "Y" (created above from Tcl) */
if ((Blt_GetVector(interp, "X", 50, &xVec) != TCL_OK) ||
(Blt_GetVector(interp, "Y", 50, &yVec) != TCL_OK)) {
return TCL_ERROR;
}

for (i = 0; i < 50; i++) {
x[i] = i * 0.02;
y[i] = sin(x[i]);
}`` ``

/* Put the data into BLT vectors */
if ((Blt_ResetVector(xVec, x, 50, 50, TCL_VOLATILE) != TCL_OK) ||
(Blt_ResetVector(yVec, y, 50, 50, TCL_VOLATILE) != TCL_OK)) {
return TCL_ERROR;
}

See the vector manual page for more details.

## Speed Tips

There may be cases where the bar chart needs to be drawn and updated as quickly as possible. If drawing speed becomes a big problem, here are a few tips to speed up displays.

·
- Try to minimize the number of data points. The more data points looked at, the more work the bar chart must do.
·
- If your data is generated as floating point values, the time required to convert the data values to and from ASCII strings can be significant, especially when there any many data points. You can avoid the redundant string-to-decimal conversions using the C API to BLT vectors.
·
- Don't stipple or dash the element. Solid bars are much faster.
·
- If you update data elements frequently, try turning off the widget's -bufferelements option. When the bar chart is first displayed, it draws data elements into an internal pixmap. The pixmap acts as a cache, so that when the bar chart needs to be redrawn again, and the data elements or coordinate axes haven't changed, the pixmap is simply copied to the screen. This is especially useful when you are using markers to highlight points and regions on the bar chart. But if the bar chart is updated frequently, changing either the element data or coordinate axes, the buffering becomes redundant.

## Limitations

Auto-scale routines do not use requested min/max limits as boundaries when the axis is logarithmically scaled.

The PostScript output generated for polygons with more than 1500 points may exceed the limits of some printers (See PostScript Language Reference Manual, page 568). The work-around is to break the polygon into separate pieces.

## Keywords

bar chart, widget

Table of Contents

- Name
- Synopsis
- Description
- Introduction
- Syntax
- Example
- Syntax
- Barchart Operations
- Barchart Components

- Axis Components
- Crosshairs Component

- Elements

- Grid Component
- Legend Component
- Pen Components
- PostScript Component
- Marker Components
- Bitmap Markers
- Image Markers
- Line Markers
- Polygon Markers
- Text Markers
- Window Markers

- Graph Component Bindings
- C Language API
- Speed Tips
- Limitations
- Keywords