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Re: Fitting a function with multiple independent variables [message #43612 is a reply to message #43609]

Wed, 20 April 2005 11:31

Craig Markwardt
Messages: 1869
Registered: November 1996

Senior Member

Sean Davis <seand@colorado.edu> writes:
> Actually, CURVEFIT does not work for that task. CURVEFIT fits a function
> with multiple parameters (a,b,c), like
>
> y = a*x + b*x^2 + c*exp(x),
>
> but not functions with multiple independent variables AND paramaters, like
>
> y = a*x1 + b*x2^2 + c*exp(x3)

This is not true. CURVEFIT does nonlinear least squares, such as your
second expression. The number of independent variables is irrelevant.
You can have no independent variables if you want! The comments here:

http://cow.physics.wisc.edu/~craigm/idl/fitqa.html#multivar

apply to CURVEFIT as well as MPFIT. Not that I am defending
CURVEFIT. :-)

Craig

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Craig B. Markwardt, Ph.D. EMAIL: craigmnet@REMOVEcow.physics.wisc.edu
Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response
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[Message index]

		Re: Fitting a function with multiple independent variables By: Sean Davis on Wed, 20 April 2005 13:02
		Re: Fitting a function with multiple independent variables By: Craig Markwardt on Wed, 20 April 2005 11:31
		Re: Fitting a function with multiple independent variables By: Sean Davis on Wed, 20 April 2005 09:30
		Re: Fitting a function with multiple independent variables By: maarten on Wed, 20 April 2005 01:06

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