Maybe a complex number structure would be good where only the real part is analyzed by pca and the imaginary part is keeping a unique id for each original pixel... On Feb 10, 2013 11:51 AM, "Markus Neteler" <nete...@osgeo.org> wrote:
> On Thu, Feb 7, 2013 at 10:21 AM, Rashad M <mohammedrasha...@gmail.com> > wrote: > > Hi, > > > > I am trying to develop a tool for grass which is one of the things that > > xgobi[1] does. The idea is from Markus Neteler which is to identify pure > > pixel/end members from a PCA plot. > > Background: it has been shown that pure pixels (endmembers) for spectral > unmixing are in the corners of the PCA feature space. > > Attached an old drawing from my master thesis (1999) about the topic. > > > Since i.pca transforms pixel position is lost. > > This is why I used the coordinates as raster pixel *attributes* in XGOBI > to relate original pixels and PCA transformed pixels to each other. > > The east, north coordinates I stored as attributes, the PCA in XGOBI > supported to keep them alongside the transformed pixel. Solved. > > What's needed in GRASS: That the i.pca modules allows to keep > raster pixel text labels in which the original position could be stored. > Then a little parsing of the category label and the original position > of a PCA transformed pixel could still be retrieved. > > Hope this explains what I did those days in my thesis. > > cheers > Markus > > _______________________________________________ > grass-dev mailing list > grass-dev@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/grass-dev >
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