# set terminal pngcairo  background "#ffffff" enhanced font "arial,10" fontscale 1.0 size 600, 400 
# set output 'pm3dcolors.9.png'
set format cb "%3.1f"
unset key
set view map
set samples 101, 101
set isosamples 2, 2
set style data pm3d
set style function pm3d
set xtics 2 norangelimit
set noytics
set noztics
set cbtics 0.1 norangelimit
set title "set palette file \"-\" (file with 3 columns)" 
set xrange [ -10.0000 : 10.0000 ] noreverse nowriteback
set cbrange [ 0.00000 : 1.00000 ] noreverse nowriteback
set pm3d explicit at b
set palette defined ( 0 0 0 0, 0.25 0 0 1, 0.5 0 1 0,\
     0.75 1 0 0, 1 1 1 1 )
g(x)=x
f(x)=(x+10)/20
GPFUN_g = "g(x)=x"
GPFUN_f = "f(x)=(x+10)/20"
splot f(x)