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Re: Fitting an implicit function with IDL [message #71291]

Wed, 09 June 2010 04:17

Gianluca Li Causi
Messages: 21
Registered: August 2005

Junior Member

>
> What I am not quite sure is how you include the data uncertainties in
> the model.

Dear Craig and Heinz,

in fact this is my problem: in the usual form F(x, A,B,C) = Y the data
uncertainties are on the right side, i.e. Y(x)+/-Err_Y(x), even if
Y=0, while in my case the data W(x) and Z(x) are within a functional
form which does not allow to isolate them on the right side.

In general if I have an equation F(x, Data(x) +/- Err_Data(x),
Params) = 0 and I try to write it as F +/- Err_F = 0, computing
Err_F as the error propagation of Err_Data through F, I get a
parameter-dependent uncertainty Err_F = Err_F(Params)!

This is why I cannot use CURVEFIT or the like (even MPFIT if I
understand). Can I?

Gianluca

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[Message index]

		Re: Fitting an implicit function with IDL By: Gianluca Li Causi on Wed, 09 June 2010 04:17
		Re: Fitting an implicit function with IDL By: Craig Markwardt on Tue, 08 June 2010 16:47
		Re: Fitting an implicit function with IDL By: Heinz Stege on Tue, 08 June 2010 15:29

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