Hi everyone,
I’d like to add the Landau fit parameters in the stats box
TF1 *Fit_ph_2 = new TF1(“ph_2”,“landau”,-1,10);
Fit_ph_2->SetLineColor(kRed);
h1->Fit(Fit_ph_2,“R+”);
Fit_ph_2->GetParameters(&par[6]);
I used that code to draw the landau fit, and
gStyle->SetOptFit(0111);
but it only shows the parameters of a Gaussian dist. fit that I applied before.
thank you.
Hi @couet
this is part of the code:
TH1 *h1 = new TH1F("Pulse charge","", 125, -10,160);
gPad-> SetLogy();
TF1 *Fit_Ped_gaus_1 = new TF1("Ped_gaus_1","gaus",Ped_gaus_1_min,Ped_gaus_1_max);
Fit_Ped_gaus_1->SetLineColor(kRed);
h1->Fit(Fit_Ped_gaus_1,"R+");
Fit_Ped_gaus_1->GetParameters(&par[0]);
TF1 *Fit_ph_2 = new TF1("ph_2","landau",landau_min,landau_max);
Fit_ph_2->SetLineColor(kRed);
h1->Fit(Fit_ph_2,"R+");
Fit_ph_2->GetParameters(&par[3]);
gStyle->SetOptFit(0111);
h1->Draw("ep*");
The problem is that I can’t find any example of how to put the Landau fit parameters in the stat box. With that code its not posible.
Thank you.
It seems fine to me:
$ root
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root [0] hpx->Fit("landau")
Info in <TCanvas::MakeDefCanvas>: created default TCanvas with name c1
FCN=10457.6 FROM MIGRAD STATUS=CONVERGED 119 CALLS 120 TOTAL
EDM=6.32046e-11 STRATEGY= 1 ERROR MATRIX UNCERTAINTY 1.6 per cent
EXT PARAMETER STEP FIRST
NO. NAME VALUE ERROR SIZE DERIVATIVE
1 Constant 4.46028e+03 5.67908e+01 1.11302e-01 3.82344e-07
2 MPV -5.78311e-01 1.23871e-02 1.91197e-05 -5.33289e-04
3 Sigma 2.81868e-01 2.94427e-03 -2.63349e-06 8.23576e-03
(TFitResultPtr) <nullptr TFitResult>
root [1] gStyle->SetOptFit(111);
yes. but if you fit with a Gaussian and then in the same histogram you fit with a Landau distribution you won’t get the parameters of the landau distr. in the stat box, you will only get the gaussian parameters in the stat box 
Not in may case. If I do:
root [0] hpx->Fit("gaus")
Info in <TCanvas::MakeDefCanvas>: created default TCanvas with name c1
FCN=63.6385 FROM MIGRAD STATUS=CONVERGED 54 CALLS 55 TOTAL
EDM=6.235e-10 STRATEGY= 1 ERROR MATRIX ACCURATE
EXT PARAMETER STEP FIRST
NO. NAME VALUE ERROR SIZE DERIVATIVE
1 Constant 8.00108e+02 6.20101e+00 1.98916e-02 -6.18780e-06
2 Mean -3.86196e-03 6.30762e-03 2.47615e-05 1.13881e-03
3 Sigma 9.94740e-01 4.45485e-03 4.77918e-06 -2.46080e-02
(TFitResultPtr) <nullptr TFitResult>
root [1] hpx->Fit("landau")
FCN=10457.6 FROM MIGRAD STATUS=CONVERGED 119 CALLS 120 TOTAL
EDM=6.32046e-11 STRATEGY= 1 ERROR MATRIX UNCERTAINTY 1.6 per cent
EXT PARAMETER STEP FIRST
NO. NAME VALUE ERROR SIZE DERIVATIVE
1 Constant 4.46028e+03 5.67908e+01 1.11302e-01 3.82344e-07
2 MPV -5.78311e-01 1.23871e-02 1.91197e-05 -5.33289e-04
3 Sigma 2.81868e-01 2.94427e-03 -2.63349e-06 8.23576e-03
(TFitResultPtr) <nullptr TFitResult>
root [2] gStyle->SetOptFit(111);
I get the same plot as before. May be provide some macro we can run to test.
what about the parameters of the gaussian ? I need both, the parameters of the gaussian and parameters of the landau in the stat box . 
that’s the problem.
ah ok … let me see… That was not clear you needed both
I think it was already answered here:
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