[GRASS-dev] Reg i.pca output

[Rashad M]

On Tue, Mar 26, 2013 at 2:44 PM, Markus Metz
<markus.metz.giswork at gmail.com>wrote:

> On Tue, Mar 26, 2013 at 8:39 AM, Rashad M <mohammedrashadkm at gmail.com>
> wrote:
> > Hi,
> >
> > i.pca creates 6 raster maps for 6 input raster
> >
> > eg:
> >
> > i.pca
> >
> in=lsat7_2002_10,lsat7_2002_20,lsat7_2002_30,lsat7_2002_40,lsat7_2002_50,lsat7_2002_70
> > \
> >     out=lsat7_2002_pca
> >
> >
> > I have a doubt here
> >
> > Does the output lsat7_2002_pca.1 is the corresponding map for
> lsat7_2002_10?
>
> No. lsat7_2002_pca.1 contains the principal component with the highest
> eigenvalue and is calculated using all input bands. More generally,
> each lsat7_2002_pca.* map is calculated using all input bands. Look at
> the eigenvectors to find out the weights with which each input map
> contributes to a specific PCA.
>
>
So by knowing a pixel value of lsat7_2002_pca.1 can I get the value before
transformation in PCA.
consider this:
I have two bands B1,B2 and after i.pca I get PC1,PC2. Then is there a way
to derive value of X,Y where X belongs to B1 and Y belongs to B2 by only
knowing P,Q
where P belongs to PC1 and Q belongs to PC2

and also X,Y and P,Q are of same index (row,col)

I hope this is clear


> Markus M
>
> >
> > If so the lsat7_2002_10_pca.1 contains PCA transformed pixel for
> > lsat7_2002_10
> >
> > Is this correct?
> >
> > --
> > Regards,
> >    Rashad
> >
> > _______________________________________________
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> > grass-dev at lists.osgeo.org
> > http://lists.osgeo.org/mailman/listinfo/grass-dev
>



-- 
Regards,
   Rashad
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