Hi, If your images are 4x3, your eigenvector must be 12 long.
Matthieu 2008/2/28, [EMAIL PROTECTED] <[EMAIL PROTECTED]>: > > i all > I am learning PCA method by reading up Turk&Petland papers etc > while trying out PCA on a set of greyscale images using python, and > numpy I tried to create eigenvectors and facespace. > > i have > facesarray--- an NXP numpy.ndarray that contains data of images > N=numof images,P=pixels in an image > avgarray --1XP array containing avg value for each pixel > adjustedfaces=facesarray-avgarray > adjustedmatrix=matrix(adjustedfaces) > adjustedmatrix_trans=adjustedmatrix.transpose() > covariancematrix =adjustedmatrix*adjustedmatrix_trans > evalues,evect=eigh(covariancematrix) > > after sorting such that most significant eigenvectors are selected. > evectmatrix is now my eigenvectors matrix > > here is a sample using 4X3 greyscale images > > evalues > [ -1.85852801e-13 6.31143639e+02 3.31182765e+03 5.29077871e+03] > evect > [[ 0.5 -0.06727772 0.6496399 -0.56871936] > [ 0.5 -0.77317718 -0.37697426 0.10043632] > [ 0.5 0.27108233 0.31014514 0.76179023] > [ 0.5 0.56937257 -0.58281078 -0.29350719]] > > evectmatrix (sorted according to largest evalue first) > [[-0.56871936 0.6496399 -0.06727772 0.5 ] > [ 0.10043632 -0.37697426 -0.77317718 0.5 ] > [ 0.76179023 0.31014514 0.27108233 0.5 ] > [-0.29350719 -0.58281078 0.56937257 0.5 ]] > > then i can create facespace by > facespace=evectmat*adjustedfaces > > till now i 've been following the steps as mentioned in the PCA > tutorial(by Lindsay smith & others) > what i want to know is that in the above evectmatrix is each row > ([-0.56871936 0.6496399 -0.06727772 0.5 ] etc) an eigenvector? > or does a column in the above matrix represent an eigenvector? > to put it differently, > should i represent an eigenvector by > evectmatrix[i] or by > (get_column_i_of(evectmatrix)).transpose() > > if someone can make this clear please do > D > _______________________________________________ > Numpy-discussion mailing list > Numpy-discussion@scipy.org > http://projects.scipy.org/mailman/listinfo/numpy-discussion > -- French PhD student Website : http://matthieu-brucher.developpez.com/ Blogs : http://matt.eifelle.com and http://blog.developpez.com/?blog=92 LinkedIn : http://www.linkedin.com/in/matthieubrucher
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