That worked. so what change the rescale option add to the transformation equation?
On Tue, Mar 26, 2013 at 7:40 PM, Markus Metz <[email protected]>wrote: > On Tue, Mar 26, 2013 at 1:21 PM, Rashad M <[email protected]> > wrote: > > It seems like values are different using the forumla. I can provide a > test > > case if you need > > > > > > > > i tried this: > > i.pca in=lsat7_2000_10,lsat7_2000_20 out=mypca > > > > Rescaling to range 0,255... > > 100% > > Eigen values, (vectors), and [percent importance]: > > PC1 436.48 ( 0.6640, 0.7477) [98.84%] > > PC2 5.13 (-0.7477, 0.6640) [ 1.16%] > > > > > > here only first column of eigen vector is important right? > > > > But let me ask does eigen values and percent of importance doesnt have > any > > role? > > > > here when running the above i.pca i get mypca.1 and mypca.2 > > P1 and P2 are first pixel row=0, col=0 of mypca.1 and mypca.2 > respectively > > and mean is the mean of lsat7_2000_10 > > > > output is the output obtained from the equation --> (X = P * > eigenvector(P, > > X) + P * eigenvector(Q, X) + mean(B1) ) > > > > and input is the pixel value of lsat7_2000_10 @ row=0, col=0 > > > > > > P1= 21 > > P2= 112 > > mean= 79.925 > > output= 138.4471 > > input= 72 > > > > Any thoughts? > > You need to disable rescaling of the PC scores with i.pca rescale=0,0 > > Markus M > > > > > > > On Tue, Mar 26, 2013 at 4:54 PM, Markus Metz < > [email protected]> > > wrote: > >> > >> 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 > > > > > > > > > > -- > > Regards, > > Rashad > -- Regards, Rashad
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