Plotchart(n) Plotchart Plotchart(n)
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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
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DESCRIPTION
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 com-pletely completely
pletely 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.
w widget (in)
Name of the existing canvas widget to hold the plot.
xaxis list (in)
A 3-element list containing minimum, maximum and stepsize for the x-axis, in this
order.
yaxis list (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.
w widget (in)
Name of the existing canvas widget to hold the plot.
xaxis list (in)
A 3-element list containing minimum, maximum and stepsize for the x-axis, in this
order.
yaxis list (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.
w widget (in)
Name of the existing canvas widget to hold the plot.
radius_data list (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.
w widget (in)
Name of the existing canvas widget to hold the plot.
xaxis list (in)
A 2-element list containing minimum, and maximum for the x-axis, in this order.
yaxis list (in)
A 2-element list containing minimum, and maximum for the y-axis, in this order.
stepsize float|noaxes (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.
w widget (in)
Name of the existing canvas widget to hold the plot.
xaxis list (in)
A 3-element list containing minimum, maximum and stepsize for the x-axis, in this
order.
yaxis list (in)
A 3-element list containing minimum, maximum and stepsize for the y-axis, in this
order.
zaxis list (in)
A 3-element list containing minimum, maximum and stepsize for the z-axis, in this
order.
::Plotchart::createPiechart w
Create a new piechart.
w widget (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 con-tained contained
tained 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.
w widget (in)
Name of the existing canvas widget to hold the plot.
xlabels list (in)
List of labels for the x-axis. Its length also determines the number of bars that will
be plotted per series.
yaxis list (in)
A 3-element list containing minimum, maximum and stepsize for the y-axis, in this
order.
noseries int|stacked (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 con-tained contained
tained 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. Oth-erwise Otherwise
erwise each series that is drawn will be drawn shifted upward.
w widget (in)
Name of the existing canvas widget to hold the plot.
ylabels list (in)
List of labels for the y-axis. Its length also determines the number of bars that will
be plotted per series.
yaxis list (in)
A 3-element list containing minimum, maximum and stepsize for the x-axis, in this
order.
noseries int|stacked (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.
w widget (in)
Name of the existing canvas widget to hold the plot.
time_begin string (in)
The start time given in a form that is recognised by the clock scan command (e.g. "1
january 2004").
time_end string (in)
The end time given in a form that is recognised by the clock scan command (e.g. "1 jan-uary january
uary 2004").
noitems int (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.
w widget (in)
Name of the existing canvas widget to hold the plot.
time_begin string (in)
The start time given in a form that is recognised by the clock scan command (e.g. "1
january 2004").
time_end string (in)
The end time given in a form that is recognised by the clock scan command (e.g. "1 jan-uary january
uary 2004").
noitems int (in)
Expected/maximum number of items. This determines the vertical spacing.
text_width int
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 com-mand: command:
mand:
$anyplot title text
Specify the title of the whole chart.
text string (in)
The text of the title to be drawn.
$anyplot saveplot filename
Draws the plot into a file, using PostScript.
filename string (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.
text string (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.
text string (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.
series string (in)
Name of the data series the new point belongs to.
xcrd float (in)
X-coordinate of the new point.
ycrd float (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.
xcrd list (in)
List of lists, each value is an x-coordinate for a grid cell corner
ycrd list (in)
List of lists, each value is an y-coordinate for a grid cell corner
values list (in)
List of lists, each value is the value at a grid cell corner
classes list (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 auto-matically. automatically.
matically.
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).
colours list (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.
xcrd list (in)
List of lists, each value is an x-coordinate for a grid cell corner
ycrd list (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.
series string (in)
Name of the data series the new point belongs to.
radius float (in)
Radial coordinate of the new point.
angle float (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).
function string (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 grid-size gridsize
size for more information).
function string (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.
contours list (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.
nxcells int (in)
Number of grid cells in x direction. Has to be an integer number greater than zero.
nycells int (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.
data list (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.
fill color (in)
The colour to use for filling the polygons.
border color (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.
series string (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 tri-angles). triangles).
angles).
For piecharts:
$pie plot data
Fill a piechart.
data list (in)
A list of pairs (labels and values). The values determine the relative size of the cir-cle circle
cle segments. The labels are drawn beside the circle.
$pie colours colour1 colour2 ...
Set the colours to be used.
colour1 color (in)
The first colour.
colour2 color (in)
The second colour, and so on.
For vertical barcharts:
$barchart plot series ydata colour
Add a data series to a barchart.
series string (in)
Name of the series the values belong to.
ydata list (in)
A list of values, one for each x-axis label.
colour color (in)
The colour of the bars.
For horizontal barcharts:
$barchart plot series xdata colour
Add a data series to a barchart.
series string (in)
Name of the series the values belong to.
xdata list (in)
A list of values, one for each y-axis label.
colour color (in)
The colour of the bars.
For timecharts:
$timechart period text time_begin time_end colour
Add a time period to the chart.
text string (in)
The text describing the period.
time_begin string (in)
Start time of the period.
time_end string (in)
Stop time of the period.
colour color (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.
text string (in)
The text describing the milestone.
time string (in)
Time at which the milestone must be positioned.
colour color (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.
text string (in)
The text appearing at the top (an abbreviation of the date/time for instance).
time string (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.
text string (in)
The text describing the task.
time_begin string (in)
Start time of the task.
time_end string (in)
Stop time of the task.
completed float (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.
text string (in)
The text describing the milestone.
time string (in)
Time at which the milestone must be positioned.
colour color (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.
text string (in)
The text appearing at the top (an abbreviation of the date/time for instance).
time string (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.
from list (in)
The list of items returned by the "task" command that represents the task from which
the arrow starts.
text string (in)
The text summarising the tasks
args list (in)
One or more tasks (the lists returned by the "task" command). They are shifted down to
make room for the summary.
to list (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!
text string (in)
The text summarising the tasks
args list (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.
keyword string (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
newcolor string (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.
keyword string (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
newfont string (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.
x1 float (in)
Minimum x coordinate of the rectangle to be drawn.
y1 float (in)
Minimum y coordinate of the rectangle.
x2 float (in)
Maximum x coordinate of the rectangle to be drawn.
y2 float (in)
Maximum y coordinate of the rectangle.
colour color (in)
The colour of the rectangle.
$isoplot plot filled-rectangle x1 y1 x2 y2 colour
Plot a rectangle filled with the given colour.
x1 float (in)
Minimum x coordinate of the rectangle to be drawn.
y1 float (in)
Minimum y coordinate of the rectangle.
x2 float (in)
Maximum x coordinate of the rectangle to be drawn.
y2 float (in)
Maximum y coordinate of the rectangle.
colour color (in)
The colour of the rectangle.
$isoplot plot circle xc yc radius colour
Plot the outline of a circle.
xc float (in)
X coordinate of the circle's centre.
yc float (in)
Y coordinate of the circle's centre.
colour color (in)
The colour of the circle.
$isoplot plot filled-circle xc yc radius colour
Plot a circle filled with the given colour.
xc float (in)
X coordinate of the circle's centre.
yc float (in)
Y coordinate of the circle's centre.
colour color (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::worldCoordi-nates. ::Plotchart::worldCoordinates.
nates.
w widget (in)
Name of the window (canvas widget) in question.
pxmin float (in)
Left-most pixel coordinate.
pymin float (in)
Top-most pixel coordinate (remember: the vertical pixel coordinate starts with 0 at the
top!).
pxmax float (in)
Right-most pixel coordinate.
pymax float (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).
w widget (in)
Name of the window (canvas widget) in question.
xmin float (in)
X-coordinate to be mapped to left side of viewport.
ymin float (in)
Y-coordinate to be mapped to bottom of viewport.
xmax float (in)
X-coordinate to be mapped to right side of viewport.
ymax float (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).
w widget (in)
Name of the window (canvas widget) in question.
xmin float (in)
X-coordinate to be mapped to front side of the 3D viewport.
ymin float (in)
Y-coordinate to be mapped to left side of the viewport.
zmin float (in)
Z-coordinate to be mapped to bottom of viewport.
xmax float (in)
X-coordinate to be mapped to back side of viewport.
ymax float (in)
Y-coordinate to be mapped to right side of viewport.
zmax float (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.
w widget (in)
Name of the window (canvas widget) in question.
x float (in)
X-coordinate to be mapped.
y float (in)
Y-coordinate to be mapped.
::Plotchart::coords3DToPixel w x y z
Return a list of pixel coordinates valid for the given window.
w widget (in)
Name of the window (canvas widget) in question.
x float (in)
X-coordinate to be mapped.
y float (in)
Y-coordinate to be mapped.
y float (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.
w widget (in)
Name of the window (canvas widget) in question.
radmax float (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.
w widget (in)
Name of the window (canvas widget) in question.
rad float (in)
Radius of the point.
phi float (in)
Angle to the positive x-axis.
::Plotchart::pixelToCoords w x y
Return a list of world coordinates valid for the given window.
w widget (in)
Name of the window (canvas widget) in question.
x float (in)
X-pixel to be mapped.
y float (in)
Y-pixel to be mapped.
::Plotchart::pixelToIndex w x y
Return the index of the pie segment containing the pixel coordinates (x,y)
w widget (in)
Name of the window (canvas widget) in question, holding a piechart.
x float (in)
X-pixel to be mapped.
y float (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, max-imum maximum
imum and stepsize that can be used for a (linear) axis.
xmin float (in)
Rough minimum value for the scaling
xmax float (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 eas-iest easiest
iest 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 sub-commands subcommands
commands 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 rou-tine routine
tine 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 pix-els pixels
els 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 calcula-tion calculation
tion 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 incor-rectly): incorrectly):
rectly):
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
3D bars, 3D surfaces, bar charts, charts, coordinate transformations, coordinates, graphical presen-tation, presentation,
tation, isometric plots, pie charts, plotting, polar plots, strip charts, time charts, xy-plots
COPYRIGHT
Copyright (c) 2004 Arjen Markus <arjenmarkus@users.sourceforge.net>
plotchart 1.1 Plotchart(n)
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