On Tue, Mar 26, 2013 at 12:10 PM, Rashad M <[email protected]> wrote: > > > > 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?
yes > >> >> 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 _______________________________________________ grass-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-dev
