graph(n) manual page

Table of Contents

## Name

eps - Encapsulated PostScript canvas item.

## Synopsis

canvas create eps x y ?option value?...

## Description

The eps canvas item lets you place encapulated PostScript (EPS) on a canvas, controlling its size and placement. The EPS item is displayed either as a solid rectangle or a preview image. The preview image is designated in one of two ways: 1) the EPS file contains an ASCII hexidecimal preview, or 2) a Tk photo image. When the canvas generates PostScript output, the EPS will be inserted with the proper translation and scaling to match that of the EPS item. So can use the canvas widget as a page layout tool.

## Example

Let's say you have for PostScript files of four graphs which you want to tile two-by-two on a single page. Maybe you'd like to annotate the graphs by putting a caption at the bottom of each graph.

Normally, you would have to resort to an external tool or write your own PostScript program. The eps canvas item lets you do this through Tk's canvas widget. An eps item displays an image (or rectangle) representing the encapsulated PostScript file. It also scales and translates the EPS file when the canvas is printed.

## Syntax

`canvas create eps x y ?option value?...
`

The eps item creates a new canvas item. Canvas is the name of a canvas widget. You must supply the X-Y coordinate of the new eps item. How the coordinate is exactly interpretered is controlled by the -anchor option (see below).

Additional options may be specified on the command line to configure aspects of the eps item such as its color, stipple, and font. The following option and value pairs are valid.

-anchor anchor
  Tells how to position the EPS item relative to its X-Y coordinate. The default is center.
-background color
  Sets the background color of the EPS rectangle.
-borderwidth pixels
  Sets the width of the 3-D border around the outside edge of the item. The -relief option determines if the border is to be drawn. The default is 0.
-file fileName
  Specifies the name of the EPS file. The first line of an EPS file must start with "%!PS" and contain a "EPS" version specification. The other requirement is that there be a "%%BoundingBox:" entry which contains four integers representing the lower-left and upper-right coordinates of the area bounding the EPS. The default is "".
-font fontName
  Specifies the font of the title. The default is *-Helvetica-Bold-R-Normal-*-18-180-*.
-foreground color
  Specifies the foreground color of the EPS rectangle. The option matters only when the -stipple option is set. The default is white.
-height pixels
  Specifies the height EPS item. If pixels is 0, then the height is determined from the PostScript "BoundingBox:" entry in the EPS file. The default is 0.
-image photo
  Specifies the name of a Tk photo image to be displayed as in the item as a preview image. This option overrides any preview specification found in the EPS file. The default is "".
-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.
-relief relief
  Specifies the 3-D effect for the EPS item. Relief specifies how the item should appear relative to canvas; for example, raised means the item should appear to protrude. The default is flat.
-shadowcolor color
  Specifies the color of the drop shadow used for the title. The option with the -shadowoffset option control how the title's drop shadow appears. The default is grey.
-shadowoffset pixels
  Specifies the offset of the drop shadow from the title's text. If pixels is 0, no shadow will be seen. The default is 0.
-showimage boolean
  Indicates whether to display the image preview (if one exists), or a simple rectangle. The default is yes.
-stipple bitmap
  Specifies a bitmap to used to stipple the rectangle representing the EPS item. The default is "".
-title string
  Sets the title of the EPS item. If string is "", then the title specified by the PostScript "Title:" entry is used. You can set the string a single space to display no title. The default is "".
-titleanchor anchor
  Tells how to position the title within EPS item. The default is n.
-titlecolor color
  Specifies the color of the title. The default is white.
-titlerotate degrees
  Sets the rotation of the title. Degrees is a real number representing the angle of rotation. The title is first rotated in space and then placed according to the -titleanchor position. The default rotation is 0.0.
-width pixels
  Specifies the width EPS item. If pixels is 0, then the width is determined from the PostScript "BoundingBox:" entry in the EPS file. The default is 0. 5i.

## Example

The graph command creates a new graph.
`# Create a new graph. Plotting area is black.
graph .g -plotbackground black
`

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

A graph has several components. To access a particular component you use the component's name. For example, to add data elements, you use the new command and the element component.
`# Create a new element named "line1"
.g element create line1 \
`` `` -xdata { 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 } \
`` `` -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 and 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 graph.
vector xVec yVec
xVec set { 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 }
yVec set { 26.18 50.46 72.85 93.31 111.86 128.47 143.14 155.85
`` `` 166.60 175.38 }
.g element create line1 -xdata xVec -ydata yVec
`

The advantage of using vectors is that when you modify one, the graph is automatically redrawn to display the new values.
`# Change the X-Y coordinates of the first point.
set xVec(0) 0.18
set yVec(0) 25.18
`

An element named line1 is now created in .g. By default, the element's label in the legend will be also line1. You can change the label, or specify no legend entry, again using the element's configure operation.
`# Don't display "line1" in the legend.
.g element configure line1 -label ""
`

You can configure more than just the element's label. An element has many attributes such as symbol type and size, dashed or solid lines, colors, line width, etc.
`.g element configure line1 -symbol square -color red \
`` `` -dashes { 2 4 2 } -linewidth 2 -pixels 2c
`

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 "line1" on the alternate Y-axis "y2".
.g element configure line1 -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.
.g 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.
`.g axis configure x -min 1.0 -max 1.5
.g axis configure y -min 12.0 -max 55.15
`

To zoom interactively, you link the axis 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 .g <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.
.g axis configure x -min {} -max {}
.g 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
.g 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.
.g legend configure -hide yes
`

The graph widget 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, images, polygons, lines, or windows. Markers can be used, for example, to mark or brush points. In this example, is a text marker that labels the data first point. Markers are created using the marker component.
`# Create a label for the first data point of "line1".
.g marker create text -name first_marker -coords { 0.2 26.18 } \
`` `` -text "start" -anchor se -xoffset -10 -yoffset -10
`

This creates a text marker named first_marker. It will display the text "start" near the coordinates of the first data point. The -anchor, -xoffset, and -yoffset options are used to display the marker above and to the left of the data point, so that the data point isn't covered by the marker. By default, markers are drawn last, on top of data. You can change this with the -under option.
`# Draw the label before elements are drawn.
.g marker configure first_marker -under yes
`

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

Finally, to get hardcopy of the graph, use the postscript component.
`# Print the graph into file "file.ps"
.g 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).

## Graph Operations

pathName axis operation ?arg?...
  See the AXIS COMPONENTS section.
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.
-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 graph 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
  Reports the size of a particular items 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 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 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.

## Graph 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 "tempAxis"
.g axis create tempAxis
`

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 tempAxis data to this axis.
.g element create "e1" -xdata $x -ydata $y -mapy tempAxis
`

While you can create many axes, only four 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 tempAxis in the left margin.
.g yaxis use tempAxis
`

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.

-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 graph is redrawn. You may query configuration options. But do not them, 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.
-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 *Graph.Axis.Color blue
option add *Graph.x.LogScale true
option add *Graph.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 graph.

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 *Graph.Crosshairs.LineWidth 2
option add *Graph.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.

### Element Components

A data element represents a set of data. It contains x and y vectors containing the coordinates of the data points. Elements can be displayed with a symbol at each data point and lines connecting the points. Elements also control the appearance of the data, such as the symbol type, line width, color 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 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 varName ?option value?... ?elemName?...
  Finds the data point closest to the window coordinates x and y in the element elemName. ElemName is the name of an element, that must not be hidden. If no elements are specified, then all visible elements are searched. It returns via the array variable varName the name of the closest element, the index of its closest point, and the graph coordinates of the point. Returns 0, if no data point within the threshold distance can be found, otherwise 1 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 graph's -halo option.
-interpolate boolean
  Indicates that both the data points and interpolated points along the line segment formed should be considered. If boolean is true, the closest line segment will be selected instead of the closest point. If this option isn't specified, boolean defaults to 0.

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.
-color color
  Sets the color of the traces connecting the data points.
-dashes dashList
  Sets the dash style of element line. DashList is a list of up to 11 numbers that alternately represent the lengths of the dashes and gaps on the element line. Each number must be between 1 and 255. If dashList is "", the lines will be solid.
-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.
-fill color
  Sets the interior color of symbols. If color is "", then the interior of the symbol is transparent. If color is defcolor, then the color will be the same as the -color option. The default is defcolor.
-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.
-linewidth pixels
  Sets the width of the connecting lines between data points. If pixels is 0, no connecting lines will be drawn between symbols. The default is 0.
-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.
-offdash color
  Sets the color of the stripes when traces are dashed (see the -dashes option). If color is "", then the "off" pixels will represent gaps instead of stripes. If color is defcolor, then the color will be the same as the -color option. The default is defcolor.
-outline color
  Sets the color or the outline around each symbol. If color is "", then no outline is drawn. If color is defcolor, then the color will be the same as the -color option. The default is defcolor.
-outlinewidth pixels
  Sets the width of the outline bordering each symbol. If pixels is 0, no outline will be drawn. The default is 1.
-pixels pixels
  Sets the size of symbols. If pixels is 0, no symbols will be drawn. The default is 0.125i.
-scalesymbols boolean
  If boolean is true, the size of the symbols drawn for elemName will change with scale of the X-axis and Y-axis. At the time this option is set, the current ranges of the axes are saved as the normalized scales (i.e scale factor is 1.0) and the element is drawn at its designated size (see the -pixels option). As the scale of the axes change, the symbol will be scaled according to the smaller of the X-axis and Y-axis scales. If boolean is false, the element's symbols are drawn at the designated size, regardless of axis scales. The default is 0.
-smooth smooth
  Specifies how connecting line segments are drawn between data points. Smooth can be either linear, step, natural, or quadratic. If smooth is linear, a single line segment is drawn, connecting both data points. When smooth is step, two line segments are drawn. The first is a horizontal line segment that steps the next X-coordinate. The second is a vertical line, moving to the next Y-coordinate. Both natural and quadratic generate multiple segments between data points. If natural, the segments are generated using a cubic spline. If quadratic, a quadratic spline is used. The default is linear.
-styles styleList
  Specifies what pen to use based on the range of weights given. StyleList is a list of style specifications. Each style specification, in turn, is a list consisting of a pen name, and optionally a minimum and maximum range. Data points whose weight (see the -weight option) falls in this range, are drawn with this pen. If no range is specified it defaults to the index of the pen in the list. Note that this affects only symbol attributes. Line attributes, such as line width, dashes, etc. are ignored.
-symbol symbol
  Specifies the symbol for data points. Symbol can be either square, circle, diamond, plus, cross, splus, scross, triangle, "" (where no symbol is drawn), or a bitmap. Bitmaps are specified as "source ?mask?", where source is the name of the bitmap, and mask is the bitmap's optional mask. The default is circle.
-trace direction
  Indicates whether connecting lines between data points (whose X-coordinate values are either increasing or decreasing) are drawn. Direction must be increasing, decreasing, or both. For example, if direction is increasing, connecting lines will be drawn only between those data points where X-coordinate values are monotonically increasing. If direction is both, connecting lines will be draw between all data points. The default is both.
-weights wVec
  Specifies the weights of the individual data points. This, with the list pen styles (see the -styles option), controls how data points are drawn. WVec is the name of a BLT vector or a list of numeric expressions representing the weights for each data point.
-xdata xVec
  Specifies the X-coordinates of the data. XVec is the name of a BLT vector or a list of numeric expressions.
-ydata yVec
  Specifies the Y-coordinates of the data. YVec 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 class is Element. The resource name is the name of the element.
`option add *Graph.Element.symbol line
option add *Graph.e1.symbol line
`

pathName element create elemName ?option value?...

  Creates a new element elemName. It's an error is an element elemName already exists. If additional arguments are present, they specify options valid for the element configure operation.
pathName element deactivate elemName ?elemName?...
  Deactivates all the elements matching pattern. Elements whose names match any of the patterns given are redrawn using their normal colors.
pathName element delete ?elemName?...
  Deletes all the named elements. The graph is automatically redrawn.
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. The default is x.
-mapy yAxis
  Specifies the Y-axis to display grid lines. YAxis must be the name of an axis. 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.

## Speed Tips

There may be cases where the graph 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 the looked at, the more work the graph 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.
·
- Data elements without symbols are drawn faster than with symbols. Set the data element's -symbol option to none. If you need to draw symbols, try using the simple symbols such as splus and scross.
·
- Don't stipple or dash the element. Solid lines are much faster.
·
- If you update data elements frequently, try turning off the widget's -bufferelements option. When the graph is first displayed, it draws data elements into an internal pixmap. The pixmap acts as a cache, so that when the graph 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 graph. But if the graph 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.

## Future Incompatibility

The -mapped options are obsoleted and will be removed. You can achieve the same results using the -hide option instead.
`# Works for now.
.g legend configure -mapped no

# Instead use this.
.g legend configure -hide yes

##

`

Keywords graph, widget

Table of Contents

- Name
- Synopsis
- Description
- Example
- Syntax
- Example
- Graph Operations
- Graph Components

- Axis Components
- Crosshairs Component
- Element Components
- Grid Component

- Speed Tips
- Limitations
- Future Incompatibility
- Keywords