Gene Expression Colormap

Returns a colormap for visualizing gene expression.

a simple function that returns a colormap, C, for visualizing gene expression. C is just a N x 3 matrix [R G B] describing the range of color values.

example usage:
C = exp_colormap('blue-yellow',64);
colormap(C);

called without any arguments, it returns a [3 x 64] green-red colormap.

options for 'colors' are:

'blue-yellow'
'green-red'
'yellow'

'N' represents the number of degrees of color to use. the default is 64.

generally speaking, the two-colored maps are appropriate for visualizing expression data which is normalized to a reference condition, e.g. to show whether expression is lower (blue or green) or higher (yellow or red) than the reference.

the single-color yellow map ('yellow') is appropriate for displaying levels of gene expression which are not compared (necessarily) to a single reference, and this is similar to the colormap used in the D-chip expression analysis software.

the colormaps returned range monotonically.