Fitting 2d data points with 1d function

ROOT
1

Dear rooters,
I need to fit this peak and more like it.

I was trying with predefined gaus but always getting Minimizer is Minuit / Migrad and Abnormal termination of minimization.

This is my code:

ntuple->Draw("x:y>>htemp","","",1,1);
htemp->Draw();
htemp->Fit("gaus","","",40,60);

I also tried:

ntuple->Draw("x:y>>htemp","","",1,1);
TProfile *prof = htemp->ProfileX();
prof->Draw();
prof->Fit("gaus","","",40,60);

and

ntuple->Draw("x:y","","",1,1);
TGraph *graph = (TGraph*)gPad->GetPrimitive("Graph");
graph->Draw();
graph->Fit("gaus","","",40,60);

and nothing works :confused:
I would greatly appreciate any help you can provide
data.root (1.92 MB)

2

ROOT has problems with negative bin contents (and “negative” peaks).
The simplest way for you is to negate “x” (i.e. take “-ch1” and/or “-ch2”), e.g.: data->Draw("-ch1:t>>htmp","","",1,1); Also, do not use the name “htemp” (ROOT uses this name “internally” on different occasions).

3

Works perfect :smiley:
Thank you so much.