[Numpy-discussion] Confused with qr decomposition function

Virgil Stokes vs@it.uu...
Mon Nov 19 17:17:53 CST 2012


I am using the latest versions of numpy (from 
numpy-1.7.0b2-win32-superpack-python2.7.exe) and scipy (from 
scipy-0.11.0-win32-superpack-python2.7.exe ) on a windows 7 (32-bit) 
platform.

I have used

import numpy as np
q,r = np.linalg.qr(A)

and compared the results obtained  from MATLAB (R2010B)

[q,r] = qr(A)

The q,r returned from numpy are both the negative of theq,r returned 
from MATLAB for the same matrix A. I believe that the q,r returned from 
MATLAB are correct. Why am I getting their negative from numpy?

Note, I have tried this on several different matrices ---  numpy always 
gives the negative of MATLAB's q,r values.
[I mistakenly have already sent a similar email to the scipy list --- 
please excuse this mistake.]


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