Re: TF2 SetRange

Could you tell me how to use this pointer? I have TH2F object:

    TH2F *histsim = new TH2F(histsimName,histsimName,256,0,256,256,0,256); and the TF2 object:

    TF2 *fitsim2_5 = new TF2("fitsim2_5",Gaus2D,0,90,50,200,5);     fitsim2_5->SetParameters(200.,30.,1.,130.,1.); then I make the fit:

    histsim->Fit("fitsim2_5","RN");

Do I do instead:

    TFitResultPtr myFit(.......)
Sorry, the usage of this function is not clear to me. Thanks, - Nevzat

> Hello Nevzat,
>
> Instead of defining your TF2 objects in that range. Do a broader range
> in the TF2 constructor and limit your fit when doing the Fit call. Use
> this member instead
>
> TFitResultPtr Fit(const char* formula, Option_t* option = "", Option_t*
> goption = "", Double_t xmin = 0, Double_t xmax = 0)
>
> cheers,
>
> John Idarraga
>
> nguler_at_jlab.org wrote:
>> Hello All,
>> I have 2D histograms with various peaks in each. I perform a gaussian fit on
>> the peaks. For the fit to be successful, I have to set x,y ranges around the
>> peaks while defining my TF2 object. Therefore, the range of my TF2 is
>> different than the range of my TH2F. This becomes problem later when I plot
>> the histogram and the fit results together on the same canvas. So, I rescale
>> the histogram by using SetRange. To be more clear, I define TH2F:
>> TH2F *histsim = new TH2F(histsimName,histsimName,256,0,256,256,0,256);
>> Then define TF2:
>> TF2 *fitsim = new TF2("fitsim",Gaus2D,0,80,75,125,5);
>> And I fit and plot:
>> histsim->Fit("fitsim","RN");
>> histsim->Draw("surf4");
>> fitsim->Draw("cont1, same");
>> But the fitsim is plotted on a different scale and does not overlap with the
>> peak anymore even if the fit is successful. So, instead I do the following:
>> histsim->Fit("fitsim","RN");
>> histsim->Draw("surf4");
>> fitsim->SetRange(0,0,256,256); //// necessary to rescale to the
>> histogram
>> range
>> fitsim->Draw("cont1, same");
>> This plots the fitsim on correct x and y positions. However, the z height of
>> the fit is still off-scale. How can I rescale the fit height so that it is
>> the
>> same as the peak height? I tried following:
>> fitsim->SetRange(0,0,0, 256,256, fitsim->GetParameter(0));
>> But it did not have any visible effect, the z range of the fit is still very
>> different than the z range of the histogram.
>>
>> I appreciate your suggestions. Thank you,
>>
>> - Nevzat Guler
>>
>>
>>
>>
>>
>

• Nevzat Guler (757) 553-8318