| Re: curvefit question [message #25745] |
Thu, 12 July 2001 08:14 |
R.G.S.
Messages: 46
Registered: September 2000
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Member |
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Mike Barker <animals@wam.umd.edu> wrote in message
news:Pine.GSO.4.21.0107111818550.4496-100000@rac4.wam.umd.ed u...
> Hello,
>
> I would like to fit the following function:
>
> y = m2*(x - x0) + m1*x0 + b1
>
> where m2 is the ONLY parameter to be fitted and m1, b1, x0 are
> variables (I DO NOT want to fit them). I'm having trouble figuring out
> how to do this with curvefit (or any of the other built-in
> routines). Curvefit won't let me pass m1, b1, and x0 as parameters. I
> tried using a common block to store the variables but I still have to
> compile the function before I declare the common block. If anyone could
> help I would be forever grateful.
>
> Sincerely,
> Mike
>
This is a BC answer (before coffee) so take it for what
its worth:
fit to
g = y - m1*x0-b1 = m2(x-x0)
hey, also change variables to (x' = x-x0)
Cheers,
bob stockwell
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| Re: curvefit question [message #25754 is a reply to message #25745] |
Wed, 11 July 2001 22:10  |
Craig Markwardt
Messages: 1869
Registered: November 1996
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Senior Member |
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david@dfanning.com (David Fanning) writes:
> Before I went to all that trouble I'd hot-foot it over
> to Craig's web page and get something better than
> CURVEFIT.
>
> http://cow.physics.wisc.edu/~craigm/idl/fitting.html
Heck, I'll agree with David on this one :-)
Mike, you'll want to check out the PARINFO keyword, and in particular
the facility to set parameters to be FIXED. Or, if you are perhaps
lazier, you can simply pass your unchanging parameters as keywords
using FUNCTARGS as Vinay described.
Craig
--
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Craig B. Markwardt, Ph.D. EMAIL: craigmnet@cow.physics.wisc.edu
Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response
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| Re: curvefit question [message #25760 is a reply to message #25758] |
Wed, 11 July 2001 16:50 |
kashyap
Messages: 26
Registered: April 1993
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Junior Member |
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Best edit CURVEFIT.PRO to include _EXTRA=E as keyword to all
calls to CALL_PROCEDURE inside it (and also to the function
definition!), then pass m1,b1,x0 as keywords to your program.
vinay
In article <Pine.GSO.4.21.0107111818550.4496-100000@rac4.wam.umd.edu>,
Mike Barker <animals@wam.umd.edu> wrote:
> Hello,
>
> I would like to fit the following function:
>
> y = m2*(x - x0) + m1*x0 + b1
>
> where m2 is the ONLY parameter to be fitted and m1, b1, x0 are
> variables (I DO NOT want to fit them). I'm having trouble figuring out
> how to do this with curvefit (or any of the other built-in
> routines). Curvefit won't let me pass m1, b1, and x0 as parameters. I
> tried using a common block to store the variables but I still have to
> compile the function before I declare the common block. If anyone could
> help I would be forever grateful.
>
> Sincerely,
> Mike
--
____________________________________________________________ __________________
kashyap@head-cfa.harvard.edu 617 495 7173 [CfA/P-146] 617 496 7173 [F]
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