TKLIB - Tk Utilities: Plotchart

NAME

Plotchart -
Simple plotting and charting package

SYNOPSIS

package require Tcl  ? 8.3 ? 
package require Tk  ? 8.3 ? 
package require Plotchart  ? 1.1 ? 
::Plotchart::createXYPlot w xaxis yaxis
::Plotchart::createStripchart w xaxis yaxis
::Plotchart::createPolarPlot w radius_data
::Plotchart::createIsometricPlot w xaxis yaxis stepsize
::Plotchart::create3DPlot w xaxis yaxis zaxis
::Plotchart::createPiechart w
::Plotchart::createBarchart w xlabels yaxis noseries
::Plotchart::createHorizontalBarchart w xlabels yaxis noseries
::Plotchart::createTimechart w time_begin time_end noitems
::Plotchart::createGanttchart w time_begin time_end noitems  ? text_width ? 
$anyplot title text
$anyplot saveplot filename
$anyplot xtext text
$anyplot ytext text
$anyplot xconfig -option value ...
$anyplot yconfig -option value ...
$xyplot plot series xcrd ycrd
$xyplot contourlines xcrd ycrd values  ? classes ? 
$xyplot contourfill xcrd ycrd values  ? classes ? 
$xyplot contourbox xcrd ycrd values  ? classes ? 
$xyplot colorMap colours
$xyplot grid xcrd ycrd
$polarplot plot series radius angle
$plot3d plotfunc function
$plot3d plotfuncont function contours
$plot3d gridsize nxcells nycells
$plot3d plotdata data
$plot3d colours fill border
$xyplot dataconfig series -option value ...
$pie plot data
$pie colours colour1 colour2 ...
$barchart plot series ydata colour
$barchart plot series xdata colour
$timechart period text time_begin time_end colour
$timechart milestone text time colour
$timechart vertline text time
$ganttchart task text time_begin time_end completed
$ganttchart milestone text time colour
$ganttchart vertline text time
$ganttchart connect from to
$ganttchart summary text args
$ganttchart color keyword newcolor
$ganttchart font keyword newfont
$isoplot plot rectangle x1 y1 x2 y2 colour
$isoplot plot filled-rectangle x1 y1 x2 y2 colour
$isoplot plot circle xc yc radius colour
$isoplot plot filled-circle xc yc radius colour
::Plotchart::viewPort w pxmin pymin pxmax pymax
::Plotchart::worldCoordinates w xmin ymin xmax ymax
::Plotchart::world3DCoordinates w xmin ymin zmin xmax ymax zmax
::Plotchart::coordsToPixel w x y
::Plotchart::coords3DToPixel w x y z
::Plotchart::polarCoordinates w radmax
::Plotchart::polarToPixel w rad phi
::Plotchart::pixelToCoords w x y
::Plotchart::pixelToIndex w x y
::Plotchart::determineScale xmin xmax

Plotchart is a Tcl-only package that focuses on the easy creation of xy-plots, barcharts and other common types of graphical presentations. The emphasis is on ease of use, rather than flexibility. The procedures that create a plot use the entire canvas window, making the layout of the plot completely automatic.

This results in the creation of an xy-plot in, say, ten lines of code:

    package require Plotchart

    canvas .c -background white -width 400 -height 200
    pack   .c -fill both

    #
    # Create the plot with its x- and y-axes
    #
    set s [::Plotchart::createXYPlot .c {0.0 100.0 10.0} {0.0 100.0 20.0}]

    foreach {x y} {0.0 32.0 10.0 50.0 25.0 60.0 78.0 11.0 } {
        $s plot series1 $x $y
    }

    $s title "Data series"

A drawback of the package might be that it does not do any data management. So if the canvas that holds the plot is to be resized, the whole plot must be redrawn. The advantage, though, is that it offers a number of plot and chart types:

XY-plots like the one shown above with any number of data series.
Stripcharts, a kind of XY-plots where the horizontal axis is adjusted automatically. The result is a kind of sliding window on the data series.
Polar plots, where the coordinates are polar instead of cartesian.
Isometric plots, where the scale of the coordinates in the two directions is always the same, i.e. a circle in world coordinates appears as a circle on the screen.
You can zoom in and out, as well as pan with these plots (Note: this works best if no axes are drawn, the zooming and panning routines do not distinguish the axes), using the mouse buttons with the control key and the arrow keys with the control key.
Piecharts, with automatic scaling to indicate the proportions.
Barcharts, with either vertical or horizontal bars, stacked bars or bars side by side.
Timecharts, where bars indicate a time period and milestones or other important moments in time are represented by triangles.
3D plots (both for displaying surfaces and 3D bars)

PLOT CREATION COMMANDS

You create the plot or chart with one single command and then fill the plot with data:

::Plotchart::createXYPlot w xaxis yaxis

Create a new xy-plot.

Type	Name	Mode
widget	w	in
	Name of the existing canvas widget to hold the plot.
list	xaxis	in
	A 3-element list containing minimum, maximum and stepsize for the x-axis, in this order.
list	yaxis	in
	A 3-element list containing minimum, maximum and stepsize for the y-axis, in this order.

::Plotchart::createStripchart w xaxis yaxis

Create a new strip chart. The only difference to a regular XY plot is that the x-axis will be automatically adjusted when the x-coordinate of a new point exceeds the maximum.

Type	Name	Mode
widget	w	in
	Name of the existing canvas widget to hold the plot.
list	xaxis	in
	A 3-element list containing minimum, maximum and stepsize for the x-axis, in this order.
list	yaxis	in
	A 3-element list containing minimum, maximum and stepsize for the y-axis, in this order.

::Plotchart::createPolarPlot w radius_data

Create a new polar plot.

Type	Name	Mode
widget	w	in
	Name of the existing canvas widget to hold the plot.
list	radius_data	in
	A 2-element list containing maximum radius and stepsize for the radial axis, in this order.

::Plotchart::createIsometricPlot w xaxis yaxis stepsize

Create a new isometric plot, where the vertical and the horizontal coordinates are scaled so that a circle will truly appear as a circle.

Type	Name	Mode
widget	w	in
	Name of the existing canvas widget to hold the plot.
list	xaxis	in
	A 2-element list containing minimum, and maximum for the x-axis, in this order.
list	yaxis	in
	A 2-element list containing minimum, and maximum for the y-axis, in this order.
float\|`noaxes`	stepsize	in
	Either the stepsize used by both axes or the keyword `noaxes` to signal the plot that it should use the full area of the widget, to not draw any of the axes.

::Plotchart::create3DPlot w xaxis yaxis zaxis

Create a new 3D plot.

Type	Name	Mode
widget	w	in
	Name of the existing canvas widget to hold the plot.
list	xaxis	in
	A 3-element list containing minimum, maximum and stepsize for the x-axis, in this order.
list	yaxis	in
	A 3-element list containing minimum, maximum and stepsize for the y-axis, in this order.
list	zaxis	in
	A 3-element list containing minimum, maximum and stepsize for the z-axis, in this order.

::Plotchart::createPiechart w

Create a new piechart.

Type	Name	Mode
widget	w	in
	Name of the existing canvas widget to hold the plot.

::Plotchart::createBarchart w xlabels yaxis noseries

Create a new barchart with vertical bars. The horizontal axis will display the labels contained in the argument xlabels. The number of series given by noseries determines both the width of the bars, and the way the series will be drawn.
If the keyword stacked was specified the series will be drawn stacked on top of each other. Otherwise each series that is drawn will be drawn shifted to the right.

Type	Name	Mode
widget	w	in
	Name of the existing canvas widget to hold the plot.
list	xlabels	in
	List of labels for the x-axis. Its length also determines the number of bars that will be plotted per series.
list	yaxis	in
	A 3-element list containing minimum, maximum and stepsize for the y-axis, in this order.
int\|`stacked`	noseries	in
	The number of data series that will be plotted. This has to be an integer number greater than zero (if `stacked` is not used).

::Plotchart::createHorizontalBarchart w xlabels yaxis noseries

Create a new barchart with horizontal bars. The vertical axis will display the labels contained in the argument ylabels. The number of series given by noseries determines both the width of the bars, and the way the series will be drawn.
If the keyword stacked was specified the series will be drawn stacked from left to right. Otherwise each series that is drawn will be drawn shifted upward.

Type	Name	Mode
widget	w	in
	Name of the existing canvas widget to hold the plot.
list	ylabels	in
	List of labels for the y-axis. Its length also determines the number of bars that will be plotted per series.
list	yaxis	in
	A 3-element list containing minimum, maximum and stepsize for the x-axis, in this order.
int\|`stacked`	noseries	in
	The number of data series that will be plotted. This has to be an integer number greater than zero (if `stacked` is not used).

::Plotchart::createTimechart w time_begin time_end noitems

Create a new timechart. The time axis (= x-axis) goes from time_begin to time_end, and the vertical spacing is determined by the number of items to plot.

Type	Name	Mode
widget	w	in
	Name of the existing canvas widget to hold the plot.
string	time_begin	in
	The start time given in a form that is recognised by the clock scan command (e.g. "1 january 2004").
string	time_end	in
	The end time given in a form that is recognised by the clock scan command (e.g. "1 january 2004").
int	noitems	in
	Expected/maximum number of items. This determines the vertical spacing.

::Plotchart::createGanttchart w time_begin time_end noitems ? text_width ?

Create a new Gantt chart. The time axis (= x-axis) goes from time_begin to time_end, and the vertical spacing is determined by the number of items to plot. Via the specific commands you can then add tasks and connections between the tasks.

Type	Name	Mode
widget	w	in
	Name of the existing canvas widget to hold the plot.
string	time_begin	in
	The start time given in a form that is recognised by the clock scan command (e.g. "1 january 2004").
string	time_end	in
	The end time given in a form that is recognised by the clock scan command (e.g. "1 january 2004").
int	noitems	in
	Expected/maximum number of items. This determines the vertical spacing.
int	text_width
	Expected/maximum width of the descriptive text (roughly in characters, for the actual space reserved for the text, it is assumed that a character is about ten pixels wide). Defaults to 20.

PLOT METHODS

Each of the creation commands explained in the last section returns the name of a new object command that can be used to manipulate the plot or chart. The subcommands available to a chart command depend on the type of the chart.

General subcommands for all types of charts. $anyplot is the command returned by the creation command:

$anyplot title text

Specify the title of the whole chart.

Type	Name	Mode
string	text	in
	The text of the title to be drawn.

$anyplot saveplot filename

Draws the plot into a file, using PostScript.

Type	Name	Mode
string	filename	in
	Contain the path name of the file to write the plot to.

$anyplot xtext text

Specify the title of the x-axis, for those plots that have a straight x-axis.

Type	Name	Mode
string	text	in
	The text of the x-axis label to be drawn.

$anyplot ytext text

Specify the title of the y-axis, for those plots that have a straight y-axis.

Type	Name	Mode
string	text	in
	The text of the y-axis label to be drawn.

$anyplot xconfig -option value ...

Set one or more configuration parameters for the x-axis. The following options are supported:

format fmt: The format for the numbers along the axis.
ticklength length: The length of the tickmarks (in pixels).
ticklines boolean: Whether to draw ticklines (true) or not (false).
scale scale_data: New scale data for the axis, i.e. a 3-element list containing minimum, maximum and stepsize for the axis, in this order.
Beware: Setting this option will clear all data from the plot.

$anyplot yconfig -option value ...

Set one or more configuration parameters for the y-axis. This method accepts the same options and values as the method xconfig.

Note: The commands xconfig and yconfig are currently implemented only for XY-plots and only the option -format has any effect.

For xy plots and stripcharts:

$xyplot plot series xcrd ycrd

Add a data point to the plot.

Type	Name	Mode
string	series	in
	Name of the data series the new point belongs to.
float	xcrd	in
	X-coordinate of the new point.
float	ycrd	in
	Y-coordinate of the new point.

For xy plots:

$xyplot contourlines xcrd ycrd values ? classes ?

Draw contour lines for the values given on the grid. The grid is defined by the xcrd and ycrd arguments (they give the x- and y-coordinates of the grid cell corners). The values are given at these corners. The classes determine which contour lines are drawn. If a value on one of the corners is missing, the contour lines in that cell will not be drawn.

Type	Name	Mode
list	xcrd	in
	List of lists, each value is an x-coordinate for a grid cell corner
list	ycrd	in
	List of lists, each value is an y-coordinate for a grid cell corner
list	values	in
	List of lists, each value is the value at a grid cell corner
list	classes	in
	List of class values or a list of lists of two elements (each inner list the class value and the colour to be used). If empty or missing, the classes are determined automatically. Note: The class values must enclose the whole range of values.

$xyplot contourfill xcrd ycrd values ? classes ?

Draw filled contours for the values given on the grid. (The use of this method is identical to the "contourlines" method).

$xyplot contourbox xcrd ycrd values ? classes ?

Draw the cells as filled quadrangles. The colour is determined from the average of the values on all four corners.

$xyplot colorMap colours

Set the colours to be used with the contour methods. The argument is either a predefined colourmap (grey/gray, jet, hot or cool) or a list of colours. When selecting the colours for actually drawing the contours, the given colours will be interpolated (based on the HLS scheme).

Type	Name	Mode
list	colours	in
	List of colour names or colour values or one of the predefined maps:

grey or gray: gray colours from dark to light
jet: rainbow colours
hot: colours from yellow via red to darkred
cool: colours from cyan via blue to magenta

$xyplot grid xcrd ycrd

Draw the grid cells as lines connecting the (valid) grid points.

Type	Name	Mode
list	xcrd	in
	List of lists, each value is an x-coordinate for a grid cell corner
list	ycrd	in
	List of lists, each value is an y-coordinate for a grid cell corner

For polar plots:

$polarplot plot series radius angle

Add a data point to the polar plot.

Type	Name	Mode
string	series	in
	Name of the data series the new point belongs to.
float	radius	in
	Radial coordinate of the new point.
float	angle	in
	Angular coordinate of the new point (in degrees).

For 3D plots:

$plot3d plotfunc function

Plot a function defined over two variables x and y. The resolution is determined by the set grid sizes (see the method gridsize for more information).

Type	Name	Mode
string	function	in
	Name of the procedure that calculates the z-value for the given x and y coordinates. The procedure has to accept two float arguments (x is first argument, y is second) and return a floating-point value.

$plot3d plotfuncont function contours

Plot a function defined over two variables x and y using the contour levels in contours to colour the surface. The resolution is determined by the set grid sizes (see the method gridsize for more information).

Type	Name	Mode
string	function	in
	Name of the procedure that calculates the z-value for the given x and y coordinates. The procedure has to accept two float arguments (x is first argument, y is second) and return a floating-point value.
list	contours	in
	List of values in ascending order that represent the contour levels (the boundaries between the colours in the contour map).

$plot3d gridsize nxcells nycells

Set the grid size in the two directions. Together they determine how many polygons will be drawn for a function plot.

Type	Name	Mode
int	nxcells	in
	Number of grid cells in x direction. Has to be an integer number greater than zero.
int	nycells	in
	Number of grid cells in y direction. Has to be an integer number greater than zero.

$plot3d plotdata data

Plot a matrix of data.

Type	Name	Mode
list	data	in
	The data to be plotted. The data has to be provided as a nested list with 2 levels. The outer list contains rows, drawn in y-direction, and each row is a list whose elements are drawn in x-direction, for the columns. Example:

    set data {
    {1.0 2.0 3.0}
    {4.0 5.0 6.0}
    }

$plot3d colours fill border

Configure the colours to use for polygon borders and inner area.

Type	Name	Mode
color	fill	in
	The colour to use for filling the polygons.
color	border	in
	The colour to use for the border of the polygons.

For xy plots, stripcharts and polar plots:

$xyplot dataconfig series -option value ...

Set the value for one or more options regarding the drawing of data of a specific series.

Type	Name	Mode
string	series	in
	Name of the data series whose configuration we are changing.

The following option are known:

colour c
color c: The colour to be used when drawing the data series.
type enum: The drawing mode chosen for the series. This can be one of line, symbol, or both.
symbol enum: What kind of symbol to draw. The value of this option is ignored when the drawing mode line was chosen. This can be one of plus, cross, circle, up (triangle pointing up), down (triangle pointing down), dot (filled circle), upfilled or downfilled (filled triangles).

For piecharts:

$pie plot data

Fill a piechart.

Type	Name	Mode
list	data	in
	A list of pairs (labels and values). The values determine the relative size of the circle segments. The labels are drawn beside the circle.

$pie colours colour1 colour2 ...

Set the colours to be used.

Type	Name	Mode
color	colour1	in
	The first colour.
color	colour2	in
	The second colour, and so on.

For vertical barcharts:

$barchart plot series ydata colour

Add a data series to a barchart.

Type	Name	Mode
string	series	in
	Name of the series the values belong to.
list	ydata	in
	A list of values, one for each x-axis label.
color	colour	in
	The colour of the bars.

For horizontal barcharts:

$barchart plot series xdata colour

Add a data series to a barchart.

Type	Name	Mode
string	series	in
	Name of the series the values belong to.
list	xdata	in
	A list of values, one for each y-axis label.
color	colour	in
	The colour of the bars.

For timecharts:

$timechart period text time_begin time_end colour

Add a time period to the chart.

Type	Name	Mode
string	text	in
	The text describing the period.
string	time_begin	in
	Start time of the period.
string	time_end	in
	Stop time of the period.
color	colour	in
	The colour of the bar (defaults to black).

$timechart milestone text time colour

Add a milestone (represented as an point-down triangle) to the chart.

Type	Name	Mode
string	text	in
	The text describing the milestone.
string	time	in
	Time at which the milestone must be positioned.
color	colour	in
	The colour of the triangle (defaults to black).

$timechart vertline text time

Add a vertical line (to indicate the start of the month for instance) to the chart.

Type	Name	Mode
string	text	in
	The text appearing at the top (an abbreviation of the date/time for instance).
string	time	in
	Time at which the line must be positioned.

For Gantt charts:

$ganttchart task text time_begin time_end completed

Add a task with its period and level of completion to the chart. Returns a list of canvas items that can be used for further manipulations, like connecting two tasks.

Type	Name	Mode
string	text	in
	The text describing the task.
string	time_begin	in
	Start time of the task.
string	time_end	in
	Stop time of the task.
float	completed	in
	The percentage of the task that is completed.

$ganttchart milestone text time colour

Add a milestone (represented as an point-down triangle) to the chart.

Type	Name	Mode
string	text	in
	The text describing the milestone.
string	time	in
	Time at which the milestone must be positioned.
color	colour	in
	The colour of the triangle (defaults to black).

$ganttchart vertline text time

Add a vertical line (to indicate the start of the month for instance) to the chart.

Type	Name	Mode
string	text	in
	The text appearing at the top (an abbreviation of the date/time for instance).
string	time	in
	Time at which the line must be positioned.

$ganttchart connect from to

Add an arrow that connects the from task with the to task.

Type	Name	Mode
list	from	in
	The list of items returned by the "task" command that represents the task from which the arrow starts.
string	text	in
	The text summarising the tasks
list	args	in
	One or more tasks (the lists returned by the "task" command). They are shifted down to make room for the summary.
list	to	in
	The list of items returned by the "task" command that represents the task at which the arrow ends.

$ganttchart summary text args

Add a summary item that spans all the tasks listed. The graphical representation is a thick bar running from the leftmost task to the rightmost.
Use this command before connecting the tasks, as the arrow would not be shifted down!

Type	Name	Mode
string	text	in
	The text summarising the tasks
list	args	in
	One or more tasks (the lists returned by the "task" command). They are shifted down to make room for the summary.

$ganttchart color keyword newcolor

Set the colour of a part of the Gantt chart. These colours hold for all items of that type.

Type	Name	Mode
string	keyword	in
	The keyword indicates which part of the Gantt chart to change:

description - the colour of the descriptive text
completed - the colour of the filled bar representing the completed part of a task
left - the colour for the part that is not yet completed
odd - the background colour for the odd entries
even - the background colour for the even entries
summary - the colour for the summary text
summarybar - the colour for the bar for a summary

Type	Name	Mode
string	newcolor	in
	The new colour for the chosen items.

$ganttchart font keyword newfont

Set the font of a part of the Gantt chart. These fonts hold for all items of that type.

Type	Name	Mode
string	keyword	in
	The keyword indicates which part of the Gantt chart to change:

description - the font used for descriptive text
summary - the font used for summaries
scale - the font used for the time scale

Type	Name	Mode
string	newfont	in
	The new font for the chosen items.

For isometric plots (to be extended):

$isoplot plot rectangle x1 y1 x2 y2 colour

Plot the outlines of a rectangle.

Type	Name	Mode
float	x1	in
	Minimum x coordinate of the rectangle to be drawn.
float	y1	in
	Minimum y coordinate of the rectangle.
float	x2	in
	Maximum x coordinate of the rectangle to be drawn.
float	y2	in
	Maximum y coordinate of the rectangle.
color	colour	in
	The colour of the rectangle.

$isoplot plot filled-rectangle x1 y1 x2 y2 colour

Plot a rectangle filled with the given colour.

Type	Name	Mode
float	x1	in
	Minimum x coordinate of the rectangle to be drawn.
float	y1	in
	Minimum y coordinate of the rectangle.
float	x2	in
	Maximum x coordinate of the rectangle to be drawn.
float	y2	in
	Maximum y coordinate of the rectangle.
color	colour	in
	The colour of the rectangle.

$isoplot plot circle xc yc radius colour

Plot the outline of a circle.

Type	Name	Mode
float	xc	in
	X coordinate of the circle's centre.
float	yc	in
	Y coordinate of the circle's centre.
color	colour	in
	The colour of the circle.

$isoplot plot filled-circle xc yc radius colour

Plot a circle filled with the given colour.

Type	Name	Mode
float	xc	in
	X coordinate of the circle's centre.
float	yc	in
	Y coordinate of the circle's centre.
color	colour	in
	The colour of the circle.

There are a number of public procedures that may be useful in specific situations: Pro memorie.

COORDINATE TRANSFORMATIONS

Besides the commands that deal with the plots and charts directly, there are a number of commands that can be used to convert world coordinates to pixels and vice versa. These include:

::Plotchart::viewPort w pxmin pymin pxmax pymax

Set the viewport for window w. Should be used in cooperation with ::Plotchart::worldCoordinates.

Type	Name	Mode
widget	w	in
	Name of the window (canvas widget) in question.
float	pxmin	in
	Left-most pixel coordinate.
float	pymin	in
	Top-most pixel coordinate (remember: the vertical pixel coordinate starts with 0 at the top!).
float	pxmax	in
	Right-most pixel coordinate.
float	pymax	in
	Bottom-most pixel coordinate.

::Plotchart::worldCoordinates w xmin ymin xmax ymax

Set the extreme world coordinates for window w. The world coordinates need not be in ascending order (i.e. xmin can be larger than xmax, so that a reversal of the x-axis is achieved).

Type	Name	Mode
widget	w	in
	Name of the window (canvas widget) in question.
float	xmin	in
	X-coordinate to be mapped to left side of viewport.
float	ymin	in
	Y-coordinate to be mapped to bottom of viewport.
float	xmax	in
	X-coordinate to be mapped to right side of viewport.
float	ymax	in
	Y-coordinate to be mapped to top side of viewport.

::Plotchart::world3DCoordinates w xmin ymin zmin xmax ymax zmax

Set the extreme three-dimensional world coordinates for window w. The world coordinates need not be in ascending order (i.e. xmin can be larger than xmax, so that a reversal of the x-axis is achieved).

Type	Name	Mode
widget	w	in
	Name of the window (canvas widget) in question.
float	xmin	in
	X-coordinate to be mapped to front side of the 3D viewport.
float	ymin	in
	Y-coordinate to be mapped to left side of the viewport.
float	zmin	in
	Z-coordinate to be mapped to bottom of viewport.
float	xmax	in
	X-coordinate to be mapped to back side of viewport.
float	ymax	in
	Y-coordinate to be mapped to right side of viewport.
float	zmax	in
	Z-coordinate to be mapped to top side of viewport.

::Plotchart::coordsToPixel w x y

Return a list of pixel coordinates valid for the given window.

Type	Name	Mode
widget	w	in
	Name of the window (canvas widget) in question.
float	x	in
	X-coordinate to be mapped.
float	y	in
	Y-coordinate to be mapped.

::Plotchart::coords3DToPixel w x y z

Return a list of pixel coordinates valid for the given window.

Type	Name	Mode
widget	w	in
	Name of the window (canvas widget) in question.
float	x	in
	X-coordinate to be mapped.
float	y	in
	Y-coordinate to be mapped.
float	y	in
	Z-coordinate to be mapped.

::Plotchart::polarCoordinates w radmax

Set the extreme polar coordinates for window w. The angle always runs from 0 to 360 degrees and the radius starts at 0. Hence you only need to give the maximum radius. Note: If the viewport is not square, this procedure will not adjust the extremes, so that would result in an elliptical plot. The creation routine for a polar plot always determines a square viewport.

Type	Name	Mode
widget	w	in
	Name of the window (canvas widget) in question.
float	radmax	in
	Maximum radius.

::Plotchart::polarToPixel w rad phi

Wrapper for a call to ::Plotchart::coordsToPixel, which assumes the world coordinates and viewport are set appropriately. Converts polar coordinates to pixel coordinates. Note: To be useful it should be accompanied by a matching ::Plotchart::worldCoordinates procedure. This is automatically taken care of in the creation routine for polar plots.

Type	Name	Mode
widget	w	in
	Name of the window (canvas widget) in question.
float	rad	in
	Radius of the point.
float	phi	in
	Angle to the positive x-axis.

::Plotchart::pixelToCoords w x y

Return a list of world coordinates valid for the given window.

Type	Name	Mode
widget	w	in
	Name of the window (canvas widget) in question.
float	x	in
	X-pixel to be mapped.
float	y	in
	Y-pixel to be mapped.

::Plotchart::pixelToIndex w x y

Return the index of the pie segment containing the pixel coordinates (x,y)

Type	Name	Mode
widget	w	in
	Name of the window (canvas widget) in question, holding a piechart.
float	x	in
	X-pixel to be mapped.
float	y	in
	Y-pixel to be mapped.

Furthermore there is a routine to determine "pretty" numbers for use with an axis:

::Plotchart::determineScale xmin xmax

Determine "pretty" numbers from the given range and return a list containing the minimum, maximum and stepsize that can be used for a (linear) axis.

Type	Name	Mode
float	xmin	in
	Rough minimum value for the scaling
float	xmax	in
	Rough maximum value for the scaling.

OTHER OUTPUT FORMATS

Besides output to the canvas on screen, the module is capable, via canvas postscript, of producing PostScript files. One may wonder whether it is possible to extend this set of output formats and the answer is "yes". This section tries to sum up the aspects of using this module for another sort of output.

One way you can create output files in a different format, is by examining the contents of the canvas after everything has been drawn and render that contents in the right form. This is probably the easiest way, as it involves nothing more than the re-creation of all the elements in the plot that are already there.

The drawback of that method is that you need to have a display, which is not always the case if you run a CGI server or something like that.

An alternative is to emulate the canvas command. For this to work, you need to know which canvas subcommands are used and what for. Obviously, the create subcommand is used to create the lines, texts and other items. But also the raise and lower subcommands are used, because with these the module can influence the drawing order - important to simulate a clipping rectangle around the axes. (The routine DrawMask is responsible for this - if the output format supports proper clipping areas, then a redefinition of this routine might just solve this).

Furthermore, the module uses the cget subcommand to find out the sizes of the canvas. A more mundane aspect of this is that the module currently assumes that the text is 14 pixels high and that 80 pixels in width suffice for the axis' labels. No "hook" is provided to customise this.

In summary:

Emulate the create subcommand to create all the items in the correct format
Emulate the cget subcommand for the options -width and -height to allow the correct calculation of the rectangle's position and size
Solve the problem of raising and lowering the items so that they are properly clipped, for instance by redefining the routine DrawMask.
Take care of the currently fixed text size properties

ROOM FOR IMPROVEMENT

In this version there are a lot of things that still need to be implemented:

General options like legends and text to the axes.
More robust handling of incorrect calls (right now the procedures may fail when called incorrectly):
- The axis drawing routines can not handle inverse axes right now.
- If the user provides an invalid date/time string, the routines simply throw an error.

TODO - SOME PRIVATE NOTES

I have the following wishlist:

Isometric plots - allow new items to be implemented easily.
Add support for histograms where the independent axis is numerical.
A general 3D viewer - emphasis on geometry, not a ray-tracer.

KEYWORDS

graphical presentation, plotting, charts, xy-plots, bar charts, strip charts, polar plots, isometric plots, pie charts, time charts, 3D surfaces, 3D bars, coordinates, coordinate transformations