Gnuplot: using custom point shapes, with legend entry

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Gnuplot provides a number of point styles to use in scatter plots, such as a cross, a star, a square, a circle etc. The available point types can be demonstrated by using the test command.

However, for a specific application, I need different symbols, and I need legend entries that show these symbols.

In particular, I need more than four symbols that can be plotted both in outlined and in filled state (e. g. triangles pointing left or right, parallelograms or non-square rectangles).

There are a number of approaches to use other shapes (each with some requirements towards the terminal, e. g. unicode support):

using PNG images
using set label '□' at 3,4 for each point, where □ can be replaced by any unicode character, such as ◁, ▶, ▭, ▮, etc.)
using plot ... with labels and providing a unicode character as a label

The problem with all of these approaches is that I can't get a proper legend (key) entry including the symbol.

I considered plotting the legend myself, but there are two reasons why I don't think that this is feasible:

For plotting the legend to the right of the chart (or at the lower right inside the chart), I would need to calculate the width of the legend, which depends on the font.
Some of the plots may include both a line and a points (like using linespoints for regular Gnuplot point types), which both have to be shown in the legend.

I am generating the Gnuplot input files programmatically, so an approach that explicitly lists all points (like the set label approach mentioned above), or that requires some calcuations, is OK.

Best Answer

This won't be an answer because I'm going to tell you to change your terminal ... I know...

There is no way to add user-defined point shape in gnuplot yet, but the PostScript terminal allows about 70 different : Postscript point types http://www.cp.cmc.osaka-u.ac.jp/~fumiko/tips/gnuplot_pt.jpg

In the following discussion, they state that there's no general mechanism to add user defined point type. And they come with the solution you gave in your question. https://groups.google.com/forum/?fromgroups=#!topic/comp.graphics.apps.gnuplot/in57UNxG2o0

I think a way to achieve your objective may be to

Use postscript to process a "human-readable" .ps file, using default point types.
"post-process" (=parse) the .ps file (it sounds like Inception to me) to change the old fashion ugly default point type into something you like, from unicode chars to home drawn shapes.
ps2pdf or ps2somethingyoulike the processed .ps file.

I'm afraid I will have to face the same problem, so let the world know if you find an easier solution :)

Related Solutions

Gnuplot: Setting the range of a third (colored) point

This is actually a really good question -- assuming you mean that you want the colorbar range to be determined (not the legend [i.e. key] -- the legend doesn't typically have that information).

My first thought was set cbrange. This might do what you want --

set cbrange [0:1500]
set palette rgbformulae 33,13,10
plot "file.dat" u 1:2:3 w p pt 7 palette

However, the question is then "What do you want to happen to out of range points?" This solution will move out of range points to the bottom/top of the scale (e.g. purple for negative numbers, red for numbers greater than 1500). My next thought was that you should be able to clip those points out by set zrange [0:1500] -- But that doesn't work. You have at least 2 options at this point.

Option 1: use splot:

set view map
set cbrange [0:1500]
set zrange [0:1500]
set palette rgbformulae 33,13,10
splot "file.dat" u 1:2:3 w p pt 7 palette

Your borders will be slightly different than they were before, but that's no real big deal.

Option 2: filter with the ternary operator (which you already know about from your previous question):

set cbrange [0:1500]
set palette rgbformulae 33,13,10
inrange(c)=((c>=0) && (c<=1500))? c : (1/0)
plot "file.dat" u 1:2:(inrange($3)) w p pt 7 palette

Also, for plotting color maps, you may want to look into the pm3d plotting style (image might work too). You might need to restructure your datafile slightly, but plotting color maps is that plotting style's bread-and-butter.

Java – Using gnuplot with java

That looks like some kind of race condition, see Java: wait for exec process till it exits. Try the following:

Runtime commandPrompt = Runtime.getRuntime();
commandPrompt.exec("gnuplot auxfile.gp");
commandPrompt.waitFor();

This should wait for the gnuplot command to finish.

Best Answer

Related Solutions

Gnuplot: Setting the range of a third (colored) point

Java – Using gnuplot with java

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