| Re: Yet another user with poly_fit problems [message #86076 is a reply to message #86074] |
Mon, 30 September 2013 13:09   |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Gus writes:
> I've read a few of the older posts on this topic, but their solution didn't really help me solve the problem that I am currently having with the poly_fit function. The set of coefficients generated by the function (a 4th degree polynomial) produces some rather absurd results. Here is a short version of the problem I am having.
>
> X = [0.000000, 11.6667, 822.914, 3458.85, 27703.4, 133928.]
> Y = [15.9000, 16.0000, 17.0000, 18.0000, 19.0000, 20.0000]
>
> C = poly_fit(X, Y, /double, yfit=D)
>
> IDL generates the following coefficients (for C)
>
> 15.940691
> 0.0015355228
> -3.0965110e-007
> 1.1170193e-011
> -6.6767399e-017
This code doesn't seem to work for me:
IDL> X = [0.000000, 11.6667, 822.914, 3458.85, 27703.4, 133928.]
IDL> Y = [15.9000, 16.0000, 17.0000, 18.0000, 19.0000, 20.0000]
IDL> C = poly_fit(X, Y, /double, yfit=D)
% Compiled module: POLY_FIT.
% Variable is undefined: NDEGREE.
Are you sure you are using the right POLY_FIT?
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/
Sepore ma de ni thue. ("Perhaps thou speakest truth.")
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