Re: How to use BestFitParameters?
- To: mathgroup at smc.vnet.net
- Subject: [mg24297] Re: How to use BestFitParameters?
- From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
- Date: Fri, 7 Jul 2000 00:11:37 -0400 (EDT)
- Organization: Universitaet Leipzig
- References: <8k0v83$q8s@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Hi,
I assume your data named p, and I will user formfun as function.
formfun = a/Sqrt[d^2 + (x1 - w0)^2];
fitres=BestFitParameters /. NonlinearRegress[
p, formfun, {x1}, {a, d, w0},
MaxIterations -> 200,
RegressionReport -> BestFitParameters
];
Now you can use the results in a plot
by
Plot[
Evaluate[formfun/. fitres],
{x1,First[p][[1]],Last[p][[1]]},
Epilog-> Point /@ p
]
I have assumed that your p data are ordered.
Regards
Jens
rob wrote:
>
> 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?
>
> Thanks, Rob