Conditional formatting in gnuplot

Question

I have thickness measurements taken on a flat plate. Is there any excel like conditional formatting option in gnuplot? I would like to have four different plots with the values,

Higher than a given number, say, in this case, 0.5
Lower than 0.5
Between a given range, say, 0.5 and 0.51
Only the values 0.5?

How to modify the codes below?

    set pm3d map
    splot 't.dat' matrix

Here is my data file

0.509   0.510   0.515   0.529   0.521   0.516   0.515
0.511   0.506   0.512   0.528   0.524   0.517   0.512
0.510   0.506   0.506   0.530   0.524   0.522   0.505
0.511   0.509   0.513   0.516   0.511   0.520   0.510
0.524   0.516   0.512   0.511   0.507   0.518   0.492
0.525   0.521   0.515   0.517   0.518   0.522   0.500
0.530   0.521   0.513   0.512   0.511   0.519   0.503
0.562   0.516   0.510   0.516   0.522   0.518   0.508
0.520   0.518   0.512   0.517   0.518   0.518   0.510
0.510   0.509   0.503   0.507   0.523   0.519   0.522
0.506   0.500   0.424   0.507   0.523   0.527   0.519
0.509   0.430   0.500   0.513   0.519   0.528   0.524
0.506   0.503   0.503   0.506   0.513   0.528   0.533
0.506   0.517   0.519   0.524   0.524   0.526   0.528
0.525   0.517   0.499   0.520   0.521   0.524   0.518
0.519   0.518   0.516   0.519   0.521   0.520   0.519
0.521   0.502   0.515   0.518   0.518   0.523   0.522
0.515   0.519   0.519   0.534   0.524   0.525   0.516
0.517   0.510   0.522   0.532   0.533   0.530   0.525
0.520   0.457   0.526   0.530   0.530   0.531   0.524
0.530   0.520   0.531   0.529   0.527   0.526   0.524

Thanks!

This can be done, but what do you want to put on the heat map for those points for which the value is outside of range? — Miguel
@Miguel, values outside the range with white color? So that looking at the plot I can have visual idea of the plate thickness condition. — kuki
@kuki Did you check my answer? Does that work for you? You can get white color either by skipping the data (second option in the answer) or by creating a palette where white is assigned to the range max or min: set palette defined (0.5 "white", 0.50000001 "black", 0.52333 "#8A2BE2", 0.54667 "red", 0.57 "yellow") then truncate the data point to that value (0.5 in this example) with a conditional plot as explained in my answer. — Miguel

Miguel Miguel · Accepted Answer · 2015-02-13T15:09:02

You can do conditional plots like this, but the conditional filtering will leave "holes" in your graph.

Without formatting:

set pm3d map
splot "./data" matrix

enter image description here

Plotting only values larger than 0.5:

set pm3d map
splot "./data" matrix u 1:2:($3 > 0.5 ? $3 : 1/0)

enter image description here

You see you have points missing. If you filter even more, you'll have more points missing, to the extreme that you might not have anything to plot (with < 0.5) because there is no way to interpolate. What you can do is substitute points outside of range by a fixed value. For instance, if the value is smaller than 0.5 substitute by 0.5, if it's larger than 0.53 substitute by 0.53:

set pm3d map
splot "./data" matrix u 1:2:($3 < 0.5 ? 0.5 : $3 > 0.53 ? 0.53 : $3)

enter image description here

For nicer display with these small matrices, you can think about interpolation:

set pm3d map interpolate 32,32
splot "./data" matrix u 1:2:($3 < 0.5 ? 0.5 : $3 > 0.53 ? 0.53 : $3)

enter image description here

Conditional formatting in gnuplot

1 Answers