The function mosaic_plot makes a mosaic plot from 2D data. One could check with
http://en.wikipedia.org/wiki/Mosaic_plot for a description of mosaic plot.
The function return two outputs xm and ym, which are the x and y components of centers of boxes. They are useful if one want to label the plot.

E.g., make a mosaic plot for random data and put the percentage of box as
label

data=rand(3,4);
[xm,ym]=mosaic_plot(data);
multi_text(xm(:),ym(:),form_percentage_strings_from_array(data(:)));