On Sunday 02 November 2003 14:21, Nadav Horesh wrote:
* Polynomials fit is relatively very simple --- you may write one of you own in less then a one day work. Since, as I said, the problem is, in many cases, unstable, you'll have the chance to implement more stable linear-equation solvers.
The polynomial fit is indeed simple, and the routine from ScientificPython that Rob uses is only 20 lines long, most of that for error checking and setting up the arrays describing the system of linear equations. Looking at the singular values in Rob's problem, I see no evidence for the problem being particularly unstable. The singular values range from 1e-6 to 1, that should not pose any problem at double precision. Moreover, for a lower-order fit that gives reasonable results, the range is only slightly smaller. So I do suspect that something goes wrong in linear_least_squares. Konrad. -- ------------------------------------------------------------------------------- Konrad Hinsen | E-Mail: hinsen@cnrs-orleans.fr Centre de Biophysique Moleculaire (CNRS) | Tel.: +33-2.38.25.56.24 Rue Charles Sadron | Fax: +33-2.38.63.15.17 45071 Orleans Cedex 2 | Deutsch/Esperanto/English/ France | Nederlands/Francais -------------------------------------------------------------------------------