Fitting non-equidistant bins histogram

[rayad]

Dear All, We have a problem to fit a non-equidistant histogram (in root file Counting.root here attached). The macro root file to do that is Counting.root also attached.

The histogram had been created, in another macro, s non-equidistant bins histogram as:
new TH1F(“Counting”,“Countingw”,NP-1,xx); where NP=150, xx[NP] is array of neutron energy, as in the attached file: .

The fit not working except at the end of the histogram. We also tried Tgraph but we have the same thing.

E_150.txt (1.8 KB)
Counting.root (4.5 KB)
Counting.C (1.8 KB)

Thank you, Rachid

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_

_ROOT Version: v6-24-02
_Platform: Ubuntu 20.04.6 LTS
_Compiler: gcc version 9.4.0

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[vpadulan]

Dear @rayad ,

Thanks for reaching out to the forum! Maybe @couet can help with your issue.

Cheers,
Vincenzo

[rayad]

Thank you Vicenzo for your answer.
Is there any thoughts about this issue, we really need to solve it to finish our results. The fitted function is needed .

Rachid

[couet]

Your macro gives me a slithly diffrent plot. but still the fits does not appear to be correct. I am looking at it.

[couet]

It seems pol3 works better:

void Counting() {
   char title1[255],title2[255],line[255];
   int i,j;
   char title[255],rootname[255];
   auto c1 = new TCanvas();

   c1->SetLogx();
   c1->SetFillColor(33);
   c1->SetFrameFillColor(41);
   c1->SetGrid();
   gStyle->SetOptFit(0);
   gStyle->SetOptStat(0);

   TFile *rootfile = new TFile("Counting.root");

   gStyle->SetOptStat(0);
   gStyle->SetTitleY(1.0); //title Y location
   gStyle->SetTitleH(0.1); //title height

   int ih;
   float myhmax;

   TH1F *counth = (TH1F *) rootfile->Get("Countingw");

   counth->SetLineStyle(20);
   counth->SetLineWidth(2);
   counth->SetLineColor(1);

   Float_t *bins = counth->GetArray();

   float minf=0,maxf=1.0e6;
   auto fitfunc = new TF1("fitfunc","pol3",minf,maxf); // Create the fit function

   counth->SetXTitle("Incident Neutron Energy(MeV)");
   counth->SetYTitle("Counts/cm^2");
   counth->SetMarkerColor(1);
   counth->SetMarkerStyle(20);
   counth->SetMarkerSize(0.7);
   counth->SetOption("P");
   counth->SetLineColor(1);
   counth->Fit("fitfunc","RQ"); // Fit histogram

   c1->SaveAs("Counting.pdf");
}