On Wed, Oct 24, 2012 at 1:33 PM, denis <denis-bz...@t-online.de> wrote: > Folks, > np.linalg.lstsq of a random-uniform A 50 x 32 with 3 columns all 0 > returns x[:3] 0 as expected, > but 4 columns all 0 => huge x: > lstsq (50, 32) with 4 columns all 0: > [ -3.7e+09 -3.6e+13 -1.9e+13 -2.9e+12 7.3e-01 ... > > This may be a roundoff problem, or even a Mac Altivec lapack bug, > not worth looking into. linalg.svd is ok though, odd. > > Summary: if you run linalg.lstsq on big arrays, > either check max |x| > or regularize, do lstsq( vstack( A, weight * eye(dim) ), > hstack( b, zeros(dim) ))
lstsq has rcond argument to do (I think) essentially the same. might need to be increased in your example. Josef > > cheers > -- denis > > _______________________________________________ > NumPy-Discussion mailing list > NumPy-Discussion@scipy.org > http://mail.scipy.org/mailman/listinfo/numpy-discussion _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
