[SciPy-user] nonlinear fit with non uniform error?
massimo sandal
massimo.sandal@unibo...
Thu Jun 21 07:31:24 CDT 2007
Matthieu Brucher ha scritto:
> I guess you refer to the distribution of the error for *each single
> point*, not the distribution of the average error in the dataset for
> different points. In this case yes, it is Gaussian, so there should be
> no problem.
> It is the distribution for all errors. If it is the same distribution
> for all points, OK with least squares. If it is not, you have to scale
> the points so that the errors follow the same gaussian law.
Sigh, there is some misunderstanding between us (surely due to my utter
ignorance).
Imagine I have three data points, A B C.
Usually, if the error is uniform (on Y) can be:
Ay +/- 5
By +/- 5
Cy +/- 5
In my case it is:
Ay +/- 5
By +/- 7
Cy +/- 11
Now, the error in all those three cases behaves gaussianly, but with
different widths.
1)Does this mean that least squares is NOT ok?
2)What does "rescaling" mean in this context?
m.
--
Massimo Sandal
University of Bologna
Department of Biochemistry "G.Moruzzi"
snail mail:
Via Irnerio 48, 40126 Bologna, Italy
email:
massimo.sandal@unibo.it
tel: +39-051-2094388
fax: +39-051-2094387
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