On Sat, Sep 17, 2011 at 10:40 AM, Charles R Harris < [email protected]> wrote:
> > > 2011/9/14 Stéfan van der Walt <[email protected]> > >> Hi all, >> >> There were some failures in the polynomial tests earlier today, and >> while investigating I saw that numpy.ma implements its own root >> finder. It uses inversion of a Van der Monde matrix, which I believe >> may suffer from some numerical instability problems. Given that >> Charles has gone to some length to implement good polynomial root >> finders, I think it would be best to employ those instead, and simply >> pre-filter the data that comes from the masked array module, if >> possible. >> >> > The test failure arises because the test compares against np.polyfit where > Travis changed the column scaling, which in turn changed the singular > values, and it is that comparison that fails. > > The Vandermonde matrix needs to be used for the fitting so nothing should > be changed there. To fix the test failure, either the test could be modified > or the ma.polyfit routine can be changed. Probably the latter is the best > option, the new scaling code can be brought over and maybe the weight and > covariance options added.Travis' changes needs to be audited in any case to > make sure all the corner cases are covered. > Note that the enhanced np.polyfit can be called directly with the weight set to zero for the masked rows, i.e., set w to the compliment of the mask. That should simplify the code a bit. Chuck
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