On Fri, 2 May 2008 23:34:19 -0700 (PDT) wilson wilson.t.thompson@gmail.com wrote:

I am trying out the eigenvectors related functions in numpy.linalg.I came across some portions where i have doubts. 1). i have an array X if i calculate L=dot(X,X.transpose()) can L be called the covariance matrix of X?I read so in a paper by Turk&Pentland(equation 3 i think) can someone clarify this ?

2). i tried to find eigenvectors using svd() and eigh() functions evects1,evals,vt=svd(L,0)

evals,evects2=eigh(L)

and sorted both evects1 and evects2 in the descending order of their evals here i find that evects1 and evects2 have same values but some of the values differ in their signs.why is this?

can anyone explain tia W _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion

http://en.wikipedia.org/wiki/Singular_value_decomposition http://en.wikipedia.org/wiki/Eigenvector http://en.wikipedia.org/wiki/Covariance_matrix

HTH,

Nils