Hi Antoine,
The only thing I can say is that your fitting function with only two
parameters does not seem appropriate or your initial parameters are
too far from the minimum.
Rene Brun
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
> fax : (757) 269 6273 \
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> --------------------------;-)
>
>
>
>
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