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

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