generate x -5,,26 32
generate y -10,,10 32
matrix z 32 32
do j=[1:32]
  do k=[1:32]
    z[k,j] = exp(-((x[j]/15)^2+(y[k]/12)^2))
  enddo
enddo
window 5
contour\legend x y z 20
window 6
set colormap thermal
density x y z
window 7
density\diffusion x y z
window 8
density\dithering x y z