i.median colortables

[Nick Cahill]

I've been trying to use i.median to produce false infrared
images from Landsat tapes, and am given error messages like
"WARNING: Histogram for [file name in PERMANENT] missing"
What produces these histograms? I've run g.support and r.stats
but neither seems to save a histogram.

A possibly related question: when I have run i.median (ignoring
the no-histogram error) the same color is applied to a number of
different data values, so that the resulting image has only a few
different colors in largish clumps. Michael Shapiro wrote a few
weeks ago that "The  number  of  colors in the color tables for raster 
maps depends only on the the number of categories in the raster map."
How does GRASS determine how many categories are in a composite
map like that produced by i.median, and is it possible to set this
number in some other way to produce a colortable with more different
values? Would the lack of a histogram cause GRASS to produce a more
limited colortable?

Thanks for any advice on this question --

Nick Cahill
nick at ikaros.harvard.edu