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Re: Minimization: Determine a constant across data sets [message #79842 is a reply to message #79829]

Fri, 06 April 2012 02:43

Mats Löfdahl
Messages: 263
Registered: January 2012

Senior Member

Den fredagen den 6:e april 2012 kl. 04:42:40 UTC+2 skrev Justin:
> Hi all!
>
> I have several data sets that follow the form:
>
> data = A* e^(-t/t0)+ y
>
> I suspect EVERY data set to have the same t0, but different A & y values. (ie: (A1,y1),(A2,y2)...)
> I can use MPFITFUN to fit A,t0 and y, but the routine determines a least chi-squared such that t0 is different for every data set.
>
> It would seem simple enough to fix t0 in MPFITFUN if I knew what the value was beforehand, but I don't :) Is there a way to minimize t0 across several data sets such that A & y are allowed to vary, but t0 is tied to every data set?

Sounds like you could describe your problem something like this:

data = [data1, data2, data3, ...]
model = [A1*e^(-t,t0)+y1, A2*e^(-t/t0)+y2, A3*e^(t/t0), ...]

If you code the model MYFUNCT with the parameter array interpreted as
p[0,1,2,3,...]=[t0,A1,y1,A2,y2,...]
you should be able to keep using mpfitfun.

/Mats

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[Message index]

		Re: Minimization: Determine a constant across data sets By: Craig Markwardt on Tue, 10 April 2012 11:24
		Re: Minimization: Determine a constant across data sets By: Justin Cantrell on Tue, 10 April 2012 07:58
		Re: Minimization: Determine a constant across data sets By: Craig Markwardt on Sat, 07 April 2012 20:05
		Re: Minimization: Determine a constant across data sets By: Mats Löfdahl on Fri, 06 April 2012 02:43

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