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MathGroup Archive 2004

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Re: NonlinearFit works not so good

  • To: mathgroup at smc.vnet.net
  • Subject: [mg49612] Re: [mg49566] NonlinearFit works not so good
  • From: DrBob <drbob at bigfoot.com>
  • Date: Sat, 24 Jul 2004 03:48:23 -0400 (EDT)
  • References: <200407231000.GAA20471@smc.vnet.net>
  • Reply-to: drbob at bigfoot.com
  • Sender: owner-wri-mathgroup at wolfram.com

The second line of code should be

data = Cases[Graphics[%], Line[x___] :> x, Infinity];

Bobby

On Fri, 23 Jul 2004 06:00:40 -0400 (EDT), Daohua Song <ds2081 at columbia.edu> wrote:

> Dear group,
>       I find the NonlinearFit give an answer far away from the truth; Here
> is an example:
>      Plot[100 Sin[3 x+1]+2,{x,0,5}];
> data=Cases[Graphics[%],Line[x___]?x,Infinity];
> <<Statistics`NonlinearFit`
> NonlinearFit[data//First,A Sin[B x+C]+D,{x},{A,B,C,D}];
> Plot[%,{x,0,5}]
> ListPlot[data//First]
>
>      If i chop the +2 from above, it works fine. but The whole thing gives
> bad fit again if you change {x,0,5}->{x,0,10}
>      So NonlinearFit also is not stable!
>      I hope it should be improved
> Daohua
>
>
>



-- 
DrBob at bigfoot.com
www.eclecticdreams.net


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