Hi rooters.
I looked at similar topics to find any answer but i couldn’t find one which worked. I’m trying to fit a distribution with a power law. I am starting from a TH2F which I project with TH2::ProfileX(). Then I define the fit function and I apply the fit
But nothing happens, even though lloking at the fit status there have been 120 iterations.
If some one has any idea bout if I would be glad to hear any advice
Thank you
Here is the code :
(part of compiled code)
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//fit function
Double_t crit_exp_fit_function(Double_t *x, Double_t *par) {
Float_t temp = x[0]-Grid_Average;
if(temp<0) {
temp = -temp;
}
return par[0](1-TMath::Power(temp/par[1],par[2]));
}
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called in
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(…)
TH2F sampler = new TH2F(“sampler”,“Data Sampler”,Grid_sizeGrid_size+1,0,Grid_sizeGrid_size,100,T_mining->cont[0],max_T);
inf_peak->Project(“sampler”,“T:N”); // building my initial TH2F with various paramters. Everything is fine looking at draws
TProfile *sampler_proj = sampler->ProfileX();
TF1 *fit = new TF1(“fit”,crit_exp_fit_function,under_mean->get_last(),over_mean->get_last(),3);
fit->SetParNames(“Tc”,“Normalization”,"#alpha");
fit->SetParameters(max_T,100,2);
(…)
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And here is the output
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FCN=0 FROM MIGRAD STATUS=CONVERGED 119 CALLS 120 TOTAL
EDM=0 STRATEGY= 1 ERROR MATRIX UNCERTAINTY 100.0 per cent
EXT PARAMETER APPROXIMATE STEP FIRST
NO. NAME VALUE ERROR SIZE DERIVATIVE
1 Tc 3.50000e+00 1.41421e+00 0.00000e+00 0.00000e+00
2 Normalization 1.00000e+02 1.41421e+00 0.00000e+00 0.00000e+00
3 #alpha 2.00000e+00 1.41421e+00 0.00000e+00 0.00000e+00
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So not any parameter changed
I joined an attachement of the TProfile drawing and the initial fit function
