How resolve gnuplot artifacts in heat map

Question

I'm trying to generate a heat map from data (https://pastebin.com/AgivvGgX). The data are not in the "matrix" form.

I tried to use pm3d map and I obtained the following plot:

I also tried to use dgrid3d and view map:

set view map
set pal def
set dgrid3d 40,40,3
splot "plot.dat" using 1:2:3 u pm3d

And I obtained the following result:

Both the plots are not correct. The dgird3d keyword creates artifacts where there are not data points.

I obtained a nice plot using the code:

set view map
set pal def
splot "plot.dat" using 1:2:3 with points pointtype 5 pointsize 1 palette   linewidth 8

Here the result

I would like to obtain a map similar to the latter one, but not with discrete points or squares but as a continuous heat map and have a white background where data are not present. Is it possible?

Michael · Accepted Answer · 2019-01-02 21:49:37Z

2

Since your data is irregular, you should use dgrid3d. It has various options (see help dgrid3d), here is a picture I've got while trying different kernels and options:

set view map
set palette defined (0 'white', 1 'blue', 2 'green', 3 'yellow', 4 'red')
set dgrid3d 100,100 exp kdensity 10,10
splot 'plot.dat' w pm3d palette

set dgrid3d 100,100 gauss kdensity 30,30
replot

edited Jan 2, 2019 at 21:49

answered Jan 2, 2019 at 21:13

Michael

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2 Comments

theozh Over a year ago

Interesting. The original data ranges from 0 to 65 but the cbrange of the plots are now 0 to 120 and <50 to 400. How to "rescale" properly depending on the kdensity values? And how to distinguish between existing values =0 and missing values? The latter now look like as they would be 0.

Simon Over a year ago

Thank you. I obtained different color code between values equal to zero and missing value using the option: set dgrid3d 100,100 hann or set dgrid3d 100,100 box

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