[R] Matrix bar plot

['Todd A. Gibson']

> -- thus distorting the perspective even more so that you can not make
> accurate (perhaps even relatively!) judgments of magnitude. I echo Hadley's
> sentiment: such 3-D bar plots are an abomination. Just because Excel can do
> them doesn't mean you should.
> 

OK, fair enough.  I am displaying several image(col=heat.colors()),
and want to show their (in)consistencies (i.e., differences between
the magnitudes).  I am loathe to use another heatmap for this as I
believe it would be confusing. One idea I suppose is to use use a
different color scheme.  Any other suggestions?
-TAG