# set terminal pngcairo  transparent enhanced font "arial,10" fontscale 1.0 size 500, 350 
# set output 'pm3dcolors.4.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 defined ( 0 \"green\", 1 \"blue\", 2 \"red\", 3 \"orange\" )" 
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 1 0, 0.3333 0 0 1, 0.6667 1 0 0,\
     1 1 0.6471 0 )
g(x)=x
f(x)=(x+10)/20
GPFUN_g = "g(x)=x"
GPFUN_f = "f(x)=(x+10)/20"
splot f(x)