Re: [ROOT] To fit a Breit Wigner

From: Ravdandorj Togoo t.62033 (togoo@sunhe.jinr.ru)
Date: Fri Nov 09 2001 - 06:21:45 MET


On Thu, 14 Jun 2001, Antoine Cazes wrote:

> 
>   Dear Rooters,
> 
>   I cannot fit an histogram with a Breit Wigner. I created a function with
> two parameters ant fited the histogram:
> 
> TF1 *bw = new TF1("bw","[0]/((x-[1])*(x-[1])+[0]/4)",0,1.4);
> h->Fit("bw");
> 
>   but the fit gives a line in the bottom of my plot and bad parameters.
> 
>   I also created a C++ function which initialize the TF1 object (like in
> the manual with the Lorenzian+background example (pages 66-67) but I get
> the same result.
> 
>   Then, I redefined the TF1 Object with 4 parameters:
> 
> TF1 *bw = new TF1("bw","[0]/((x-[2])*(x-[3])+[1]/4)",0,1.4);
> h->Fit("bw");
> 
>   The fit look great in the screen, except that the parameters 0 and 1 or
> 2 and 3 are totally different.
> 
>   I use Root 3.0 on a Linux machine (RedHat 6.2)
> 
>   Thanks for your help,
> 
> 	Antoine Cazes
> 
> -------------------------------------
> Thomas Jefferson National Laboratory \
> Office 71 trailer 16                  \  Institution: University of
> Phone: (757) 269 5551                  \              South Carolina
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> 
> 
> 
> 



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