[SciPy-Dev] parameters of fitting data

josef.pktd@gmai... josef.pktd@gmai...
Tue Nov 22 16:22:57 CST 2011


On Tue, Nov 22, 2011 at 3:56 PM, Krzysztof Berniak
<krzysztof.berniak@gmail.com> wrote:
> Hello,
>   I'm writing script in python, which fitting exponencial curve to data (
> f(x) = a*exp(x*b).
>  To resolve this problem I use scipy.
>  It works fine. I get in v1 new parameters, but where is calculation errors
> of this parameters ?
> When I use gnuplot my results look like this:
> Final set of parameters            Asymptotic Standard Error
> =======================            ==========================
> a1              = 12.1566                                   +/- 0.2286
> (1.88%)
> b1              = 0.000858396                           +/- 4.362e-006
> (0.5082%)
>
>   ^
>
>
>   |
>                                                                where in
> scipy i get this numbers
> This is my code
> def main():
>     z,f = numbers_col()
>     fitfunc = lambda v, z: v[0]*exp(z*v[1])
>     errfunc = lambda v, z,f: fitfunc(v,z) - f
>     v0 = [10., 0.005]
>     v1,success = optimize.leastsq(errfunc, v0[:], args =
> (z,f),full_output=True)
> regards and please help,
> Cristopher

use optimize.curvefit which returns the covariance matrix for the
parameter estimates, and np.sqrt(np.diag(cov)) gives the standard
errors for each parameter estimate.

Josef

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