[GRASS-dev] i.pca

[Michael Barton]

Thanks. That makes my life much easier for this.

Michael.


On 2/23/07 3:01 AM, "Brad Douglas" <rez at touchofmadness.com> wrote:

> Michael,
> 
> ASTER L1B data allocates 0 for dummy or null cells.  1 is reserved for
> areas of zero radiance.  These and other values are defined in the ASTER
> Users Handbook and is consistent with my experience.
> 
> You shouldn't have to go through all the extra effort to ensure deep
> absorbers are 'visible'.
> 
> On Fri, 2007-02-23 at 01:08 -0700, Michael Barton wrote:
>> 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