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Re: What to give as "real column vector of initial parameters" to nonlin

From: Dmitri A. Sergatskov
Subject: Re: What to give as "real column vector of initial parameters" to nonlin_curvefit?
Date: Fri, 12 Jun 2020 14:31:47 -0400


On Fri, Jun 12, 2020 at 2:17 PM Doron Behar <doron.behar@gmail.com> wrote:


What do you mean by similar to each other?

I hate typing and it is hard to explain in a few words.
Non-linear fitting is an art...
In your example
M*sin(W*t+phi) vs A*sin(W*t) + B*cos(W*t)

Parameters A and B are more similar than M and phi.
The change in function values wrt A and B are similar.
The change in function values wrt M and phi is vastly different
(one is monotonic, another is periodic). Generally speaking you want your
function of parameters value as linear as possible.

Dmitri.
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