I am struggling with the following problem. I have a file with three columns, the x-coord, y-coord and count; think of it as of a sparse histogram, where a point is outputted only when count > 0.
I am trying to visualize it using GNUPLOT via
set palette defined (0 'white', 0.25 'blue', 0.5 'green', 0.75 'yellow', 1 'red')
plot 'file' w p pt 7 palette t ''
which works just fine. Now, I would like to have a logarithmic color box, that is so that the colors are mapped to log(count). I could trick it through u 1:2:(log($3)), but the scale on the color box would be off.
Using set log cb actually gives me an error: GNUPLOT complains that the data is negative, which it is not, I have hand-checked the offending file. This is the error I get from a cut-down version of the file,
gnuplot> set logscale cb
gnuplot> plot 'data.dat' w p pt 7 palette
Warning: empty x range [-0.226728:-0.226728], adjusting to [-0.228995:-0.22446]
color axis has cb coord of -3.20125; must be above 0 for log scale!
The data file is actually very small:
-2.2672752051521861e-01 -9.0322580645161288e-01 1.2583021897450098e-03
-2.2672752051521861e-01 -8.3870967741935487e-01 1.2583021897450098e-02
-2.2672752051521861e-01 -7.7419354838709675e-01 6.2915109487250492e-03
-2.2672752051521861e-01 -7.0967741935483875e-01 1.0066417517960079e-02
-2.2672752051521861e-01 -6.4516129032258063e-01 1.0066417517960079e-02
-2.2672752051521861e-01 -5.8064516129032262e-01 3.7749065692350295e-03
-2.2672752051521861e-01 -5.1612903225806450e-01 6.2915109487250492e-03
-2.2672752051521861e-01 -4.5161290322580649e-01 2.5166043794900197e-03
-2.2672752051521861e-01 -3.8709677419354838e-01 4.4040576641075340e-03
-2.2672752051521861e-01 -3.2258064516129037e-01 2.5166043794900197e-03
-2.2672752051521861e-01 -2.5806451612903225e-01 1.2583021897450098e-03
-2.2672752051521861e-01 -1.9354838709677424e-01 3.1457554743625246e-03
-2.2672752051521861e-01 -1.2903225806451613e-01 6.2915109487250492e-04
-2.2672752051521861e-01 -6.4516129032258118e-02 1.2583021897450098e-03
-2.2672752051521861e-01 0.0000000000000000e+00 4.4040576641075340e-03
-2.2672752051521861e-01 6.4516129032258007e-02 1.2583021897450098e-03
-2.2672752051521861e-01 1.2903225806451601e-01 1.8874532846175148e-03
-2.2672752051521861e-01 1.9354838709677424e-01 3.1457554743625246e-03
-2.2672752051521861e-01 3.2258064516129026e-01 1.2583021897450098e-03
-2.2672752051521861e-01 3.8709677419354827e-01 2.5166043794900197e-03
-2.2672752051521861e-01 4.5161290322580649e-01 3.7749065692350295e-03
-2.2672752051521861e-01 5.1612903225806450e-01 5.6623598538525447e-03
-2.2672752051521861e-01 5.8064516129032251e-01 6.2915109487250492e-03
-2.2672752051521861e-01 6.4516129032258052e-01 6.9206620435975537e-03
What's wrong?