Gnuplot filledcurves with palette

Question

I have been trying to change the fillstyle for the filledcurves option in gnuplot so that the fill colour represents the difference between the two curves on a 2-dimensional

Answer 1

The trick is to draw the lines, then fill between them with filledcurves. Here's how to do it (based on the examples at gnuplot):

set style line 2 lc rgb 'forest-green'
set style line 3 lc rgb 'plum'
set style fill pattern 5 lc 'yellow'
set xrange [0:3000]
set yrange [0:1]
plot 'data.txt' u 1:2:3 w filledcurves notitle, \
     '' u 1:2 ls 2 with lines notitle, \
     '' u 1:3 ls 3 with lines notitle

The output looks like this:

The data file contains these dummy values (that resemble your second graph):

500     0.90    0.90
1000    0.90    0.75
1500    0.92    0.40
2000    0.95    0.30
2500    0.94    0.23