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Re: Help with least squares on non-linear function [message #85664 is a reply to message #85661]

Sun, 25 August 2013 05:40

Heinz Stege
Messages: 189
Registered: January 2003

Senior Member

On Sat, 24 Aug 2013 14:53:39 -0700 (PDT), Phillip Bitzer wrote:

> Yep, that was the next piece of advice :-) MPFIT is highly recommended....

I would say, this is a linear function. Here is a way how to calculate
the fit parameters.

Put your x, k and y values into the arrays
x=dblarr(npoints)
k=dblarr(npoints)
y=dblarr(npoints)

With npars=3, create the matrix
fx=dblarr(npoints,npars)
for i=1,npars do fx[0,i-1]=((1+k)^i-k^i)*x^i

and do the calculation
temp=transpose(fx)
a=temp#fx
b=temp#y
ludc,a,indx
par=lusol(a,indx,b)

par is an array with npars elements and should contain the fit
parameters named by a_i within your function.

I hope, that there is no error in this code. I couldn't test it,
because I have no example values for x, k and y.

Cheers, Heinz

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[Message index]

		Help with least squares on non-linear function By: stefan.meingast on Sat, 24 August 2013 12:14
		Re: Help with least squares on non-linear function By: stefan.meingast on Sat, 24 August 2013 12:20
		Re: Help with least squares on non-linear function By: Phillip Bitzer on Sat, 24 August 2013 14:10
		Re: Help with least squares on non-linear function By: stefan.meingast on Sat, 24 August 2013 14:32
		Re: Help with least squares on non-linear function By: Phillip Bitzer on Sat, 24 August 2013 14:53
		Re: Help with least squares on non-linear function By: Heinz Stege on Sun, 25 August 2013 05:40

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