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MathGroup Archive 2000

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Re: How to use BestFitParameters?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg24283] Re: [mg24274] How to use BestFitParameters?
  • From: BobHanlon at aol.com
  • Date: Fri, 7 Jul 2000 00:11:25 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

In a message dated 7/5/2000 11:39:23 PM, piovere at pdq.net writes:

>p is a list of data pairs { {x1,y1}, {x2,y2}, ....} and when I fit
>this data to a function Mathematica does a pretty good job of doing the
>fit:
>
>NonlinearRegress[p, a/Sqrt[d^2 + (x1 - w0)^2], {x1}, {a, d, w0}, 
>  MaxIterations -> 200, RegressionReport -> BestFitParameters]
>
>gives this as an output:
>{BestFitParameters -> {a -> 1.07061, d -> 0.300272, w0 -> 28.8068}}
>
>I know it is pretty a pretty good fit to the data because I can use
>another program like Excel to plot the curve using these parameters
>and display it next to the data.  It sure would be nice to do this in
>Mathematica without going to an outside program.  I've tried things but
>I
>can't seem to be able to get to the parameters a, d and w0.  I can't
>even list them.  For example,  I'd like to display the number
>d/Sqrt[w0^2-d^2]. So I tried this:
>
>d/Sqrt[w0^2-d^2] /. %
>
>All I get is the formula in symbolic form.
>
>Can someone here provide some relief?
>

d/Sqrt[w0^2-d^2] /. (BestFitParameters /. %)

Bob Hanlon


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