[SciPy-user] Re: Eror estimation in leastsq

Travis Oliphant oliphant.travis at ieee.org
Thu Feb 21 11:50:56 CST 2002


On Thursday 21 February 2002 08:16 am, you wrote:
> The problem is indeed nonlinear (iterative) least-squares fit. I looked
> at two places:
>
>    1. Gnuplot: There estimation is given by: err[i] =
>       sqrt(covariance[i][i] * chi_sqr) / (free_degrees_of_freedom).
>    2. Numerical recipes book (chapter 15.6): Highly recommends against
>       the above method for nonlinear fittings, and suggests more
>       elaborate methods such as bootstrapping.
>
> Trying to be not to religious, I read minpack documentation looking a
> way to implement the Gnuplot's attitude, but I could not understand how
> to get the covariance matrix.

I suspect that it could be obtained from the variables in infodict (use 
full_output=1) (see help(optimize.minpack)).  If you figure out how to get 
them from the information in there let us know so we can add it.  

-Travis






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