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Re: curvefit [message #44437 is a reply to message #9041]

Mon, 13 June 2005 14:50

kashyap
Messages: 26
Registered: April 1993

Junior Member

In article <1118691431.765056.244800@f14g2000cwb.googlegroups.com>,
<nolan.smith1@gmail.com> wrote:
> Hello,
>
> I am new in IDL and I am trying to fit my data (x,y coordinates) in a
> function of this form:
>
> y(x)=A/[(1+x/B)^1/2]^2
>
> so that I can calculate A and B.
>
> I have read the documentation but I am very confused as to how I should
> set up my function to use it at the curvefit.
> Could you please explain to me how to set up the function and how to
> use curvefit correctly?
>
> Thank you,
> Nolan Smith
>

Create a new procedure, say testfun.pro:

pro testfun,x,y,par,dfdpar
y=par[0]/((1+x/par[1])^(1./2.))^2
;question: why is this not y=par[0]/(1+x/par[1]) ?
dfdpar=fltarr(n_elements(x),2)
dfdpar[*,0]=y/par[0]
dfdpar[*,1]= {partial}y/{partial}B ..
;calculation left as an exercise for the reader!
return
end

and then call curvefit as
yfit=curvefit(x,y,weights,par,function_name='testfun')

vinay
--
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kashyap@head.cfa.harvard.edu 617 495 7173 [CfA/P-145] 617 496 7173 [F]

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[Message index]

		Curvefit By: zanotti on Wed, 21 May 1997 00:00
		Re: Curvefit By: thompson on Wed, 21 May 1997 00:00
		Re: curvefit By: David Fanning on Tue, 07 January 2003 20:13
		Re: CURVEFIT By: Craig Markwardt on Wed, 02 June 2004 11:40
		Re: CURVEFIT By: K. Bowman on Wed, 02 June 2004 08:56
		Re: curvefit By: Paolo Grigis on Tue, 14 June 2005 09:16
		Re: curvefit By: nolan.smith1 on Tue, 14 June 2005 08:20
		Re: curvefit By: nolan.smith1 on Mon, 13 June 2005 21:02
		Re: curvefit By: nolan.smith1 on Mon, 13 June 2005 20:07
		Re: curvefit By: Craig Markwardt on Mon, 13 June 2005 15:24
		Re: curvefit By: kashyap on Mon, 13 June 2005 14:50
		Re: curvefit By: nolan.smith1 on Mon, 13 June 2005 12:59
		Re: curvefit By: Benjamin Hornberger on Mon, 13 June 2005 12:46

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