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Re: Fitting curves [message #2880 is a reply to message #2707]

Fri, 02 September 1994 13:08

isaacman
Messages: 20
Registered: June 1992

Junior Member

In article <CvIEz3.K5o@usenet.ucs.indiana.edu>, amaravad@silver.ucs.indiana.edu (ratnakar amaravadi) writes...
> In article <341uu7$9me@aragorn.unibe.ch> larkum@optolab.unibe.ch writes:
>> Hi,
>>
>> I know this goes around once in a while but I'm really confused about
>> how to use the CURVEFIT procedure. I want to fit a double or triple
> ^^^^^^^^^^^^^^^^^^^^^^
>> exponential curve to some data. Inititally, I'll be happy to try
> ^^^^^^^^^^^^^^^^^^
>> out a single exponential fit.
>>
>
> pardon my ignorance, but do you mean a sum of 2 or 3 exponentials :
> like Y(x) = A*exp(Bx)+C*exp(Dx). If this is what you want to do,
> it is fairly straight forward with the CURVEFIT procedure. For better
> understanding try reading the Marquartdt algorithm from Bevington.
> This book is refered to in the help pages of IDL's CURVEFIT routine.

Be very careful in your choice of both minimization algorithm and
initial guess parameters for this function! It can be VERY
ill-conditioned.

Rich Isaacman
General Sciences Corp.
NASA/Goddard Space Flight Center
Code 902.3

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[Message index]

		Fitting curves By: larkum on Wed, 31 August 1994 06:00
		Re: Fitting curves By: larkum on Tue, 06 September 1994 01:03
		Re: Fitting curves By: agraps on Fri, 02 September 1994 17:52
		Re: Fitting curves By: isaacman on Fri, 02 September 1994 13:08
		Re: Fitting curves By: amaravad on Fri, 02 September 1994 08:57

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