linear blue colormap
cmap=oceancolormap(n)
:n integer >= 3, the colormap size. : :cmap matrix with 3 columns [R,G,B]. :
oceancolormap computes a colormap with with n blue colors varying linearly from black to white.
f = `scf`_();
`plot3d1`_();
f.color_map = oceancolormap(32);