# set terminal png transparent nocrop enhanced font arial 8 size 420,320 
# set output 'pm3d.9.png'
set border 4095 lt -1 lw 1.000
set view map
set samples 50, 50
set isosamples 50, 50
unset surface
set style data pm3d
set style function pm3d
set ticslevel 0
set title "colour map, using default rgbformulae 7,5,15 ... traditional pm3d (black-blue-red-yellow)" 0.000000,0.000000  font ""
set xlabel "x" 0.000000,0.000000  font ""
set xrange [ -15.0000 : 15.0000 ] noreverse nowriteback
set ylabel "y" 0.000000,0.000000  font ""
set yrange [ -15.0000 : 15.0000 ] reverse nowriteback
set y2range [ * : * ] reverse nowriteback  # (currently [-10.0000:10.0000] )
set zrange [ -0.250000 : 1.00000 ] noreverse nowriteback
set pm3d at b
splot sin(sqrt(x**2+y**2))/sqrt(x**2+y**2)