On Tue, Mar 26, 2013 at 3:58 PM, Markus Metz <[email protected]>wrote:
> On Tue, Mar 26, 2013 at 10:25 AM, Rashad M <[email protected]> > wrote: > > > > > > > > On Tue, Mar 26, 2013 at 2:44 PM, Markus Metz < > [email protected]> > > wrote: > >> > >> On Tue, Mar 26, 2013 at 8:39 AM, Rashad M <[email protected]> > >> 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) > > X = P * eigenvector(P, X) + P * eigenvector(Q, X) + mean(B1) > > Using the example from the manual: > > X = 0.2824 * PC1 + 0.2541 * PC2 + 0.3801 * PC3 + 0.1752 * PC4 - > 0.6170 * PC5 - 0.5475 * PC6 + mean(band 1) > Thanks. just a small clarification: PC1 is the pixel value at (i,j) of output band pca.1 and X is the pixel value at (i,j) of input band b1 This is correct? > Markus M > > > > > 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 > >> > > >> > _______________________________________________ > >> > grass-dev mailing list > >> > [email protected] > >> > http://lists.osgeo.org/mailman/listinfo/grass-dev > > > > > > > > > > -- > > Regards, > > Rashad > -- Regards, Rashad
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