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Re: 3D Curve Fitting [message #62747 is a reply to message #62744]

Wed, 01 October 2008 10:07

Craig Markwardt
Messages: 1869
Registered: November 1996

Senior Member

Wox <nomail@hotmail.com> writes:
>
> Sorry for the confusing, it must be: "If you have 3 DEPENDENT
> variables, you can't use mpfit or curvefit or whatever"

I don't think your claim is correct. If you have the independent
variable, X, and *two* measurements per X point, (say Y and Z) then it
is straightforward to fit both of those points simultaneously. That
is effectively fitting a 2D function. The method is the same,
MPFITFUN('MYFUNCT', X, [Y, Z], [ERR_Y, ERR_Z], ...)
and your function is responsible for computing both functions
separately and then stacking them together.

> The point is, mpfit (and all curvefitting routines) can handle only 1
> dependent variable and any number if independent variables.

Again, not true, see above.

However, your original request was entirely different. You wanted to
fit a "quartic" curve through some "points in 3D space." Again, a
quartic function of what? Define your problem first, please.

Craig

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Craig B. Markwardt, Ph.D. EMAIL: cbmarkwardt+usenet@gmail.com
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[Message index]

		Re: 3D Curve Fitting By: Craig Markwardt on Thu, 02 October 2008 09:05
		Re: 3D Curve Fitting By: Craig Markwardt on Thu, 02 October 2008 09:01
		Re: 3D Curve Fitting By: Wox on Thu, 02 October 2008 04:50
		Re: 3D Curve Fitting By: Wox on Thu, 02 October 2008 04:13
		Re: 3D Curve Fitting By: jaz on Thu, 02 October 2008 02:59
		Re: 3D Curve Fitting By: R.G. Stockwell on Wed, 01 October 2008 11:04
		Re: 3D Curve Fitting By: Craig Markwardt on Wed, 01 October 2008 10:07
		Re: 3D Curve Fitting By: Craig Markwardt on Wed, 01 October 2008 09:53
		Re: 3D Curve Fitting By: jameskuyper on Wed, 01 October 2008 06:07
		Re: 3D Curve Fitting By: David Fanning on Wed, 01 October 2008 05:19
		Re: 3D Curve Fitting By: Wox on Wed, 01 October 2008 05:04
		Re: 3D Curve Fitting By: Wox on Wed, 01 October 2008 04:50
		Re: 3D Curve Fitting By: Rob.Dimeo on Wed, 01 October 2008 04:08
		Re: 3D Curve Fitting By: Wox on Wed, 01 October 2008 01:55
		Re: 3D Curve Fitting By: jaz on Wed, 01 October 2008 00:35
		Re: 3D Curve Fitting By: russell.grew on Tue, 30 September 2008 17:15

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