POLARMAP: Polarized colormap

Colormap with zero-center white shading.

When representing "polarized" data for which zero and sign are meaningful (like for instance, a gravity anomalies map), it is useful to have a colormap where white stands for zero value, and greater magnitudes are plotted as colors with increasing saturation.

This little function POLARMAP has two different usages:

- proposes a new red-white-blue colormap that is standard for this purpose (same usage as other Matlab colormaps);

- applies a zero-center white shading to any existing colormap, like JET or HSV, or user defined.

Type "doc polarmap" for complete help, syntax and examples.