| Re: Help with SVDFIT (newbe) [message #7031] |
Thu, 12 September 1996 00:00 |
Christian Soeller
Messages: 46
Registered: August 1996
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Member |
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"H.Greeley" <hal_greeley@valley.net> writes:
>
> I am trying to fit an exponential using SVDFIT. Could someone give me a
> fairly detailed example of how to use the FUNCT parameter .
Instead of supplying an example I would suggest you had a look at the relevant
chapter about Modelling of Data in NUMERICAL RECIPES in C(FORTRAN, PASCAL,
etc). Section 15.4 (General Linear Least Squares) and subsection
Solution by Use of Singular Value Decomposition therein explain what
the user supplied function (FUNC in IDL) should do, namely evaluate
the M basis functions (e.g. polynomials, cosines, etc) at the supplied
N input points and return an (N,M) array of results. See also the
documentation at the beginning of the idl source code (i.e., type
DOC_LIBRARY,'SVDFIT' at the IDL prompt).
Regards,
Christian
PS. Are you sure you want to do a multidimensional fit? Otherwise you're
better off using the function CURVEFIT for your fitting problem. I can send
you an example of using curvefit if required.
------------------------------------------------------------ --------
Christian Soeller mailto: csoelle@sghms.ac.uk
St. Georges Hospital Medical School Dept. of Pharmacology
Cranmer Terrace London SW17 0RE
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