[GRASS-dev] i.pca

[Michael Barton]

Good point. But I can't just set 0=NULL, because there might well be 0's
that mean something (e.g., water). If I really wanted to work with this
image, I'd probably have to make a 'null mask' with the map calculator,
setting to null any pixel that is 0 in all bands, and setting the rest to 1.
Then I multiply each image by the null mask. If you have a faster way, I'd
love to know about it.

Michael


On 2/22/07 11:27 PM, "Brad Douglas" <rez at touchofmadness.com> wrote:

> Is the pinkish area on the right edge supposed to be NULL data?  If so,
> I would make sure you ran 'r.null setnull=0'.  The non-null data may
> skew your results, slightly.  This was one of my motivations for the
> rewrite.

__________________________________________
Michael Barton, Professor of Anthropology
School of Human Evolution & Social Change
Center for Social Dynamics & Complexity
Arizona State University

phone: 480-965-6213
fax: 480-965-7671
www: http://www.public.asu.edu/~cmbarton