# set terminal canvas  solid butt size 600,400 fsize 10 lw 1 fontscale 1 name "discrete_2" jsdir "."
# set output 'discrete.2.js'
set contour base
set cntrparam levels discrete 0,15 ,75 
set title "3 discrete contours at 0 15 & 75" 
splot x*y