Hi Danilo,
I do no see you actually fill the histogram.
Anyhow, it seems to me that you really want to fit a TGraphErrors
object. SO in your test_2 fill the TGraphError like
in you modified hsimple.C and give the same Fit command (which
is also a member function of TGraph...)
> X-Authentication-Warning: newmint.cern.ch: Host thsun1-3.jinr.ru [159.93.23.2]
claimed to be thsun1.jinr.ru
> Date: Tue, 17 Jul 2001 21:10:01 +0400 (MSD)
> From: Danilo Behnke <behnke@thsun1.jinr.ru>
> X-Sender: behnke@thsun1
> To: roottalk@pcroot.cern.ch
> cc: Danilo Behnke <danilo.behnke@physik.uni-rostock.de>
> Subject: [ROOT] fit-function
> MIME-Version: 1.0
> X-Filter-Version: 1.3 (wren)
>
> Hi ROOTers,
>
> in order to fit some data I rewrote the example-files myfit.C and
> hsimple.C. Here I have to fit no histogram but some data-points. But as
> far as I recognized, that should be nearly the same. I tried to fit with a
> simple linear term (because I wanted to get familiar with user defined
> function), but I did not get what I expected (but a straight line on the
> x-axis).
> What maybe the mistake? And could you give me an advice, how to implement
> an integral (with 2 or 3 parameters) as my fit function?
> Thank you for your effort, maybe I am not able to read the manual
> correct...
>
> Danilo
>
>
> This is my modified myfit.C
>
> Double_t fitfunc(Double_t *x, Double_t *par)
> {
> Double_t fitval = par[0]+x[0]*par[1]+x[0]*x[0]*par[2];
> return fitval;
> }
> gRoot->Reset();
> //this function used fitfunc to fit a graph
> void test_2()
> {
> TFile *f = new TFile("daten.root");
> TH1F *data = (TH1F*)f->Get("data");
> TF1 *function = new TF1("fitfunc","fitfunc",0,1,3);
> function->SetParNames("const","linear","quadratic");
> data->Fit(function,"R");
> }
>
> And this is the modified hsimple.C
>
> {
> gROOT->Reset();
>
> c1 = new TCanvas("c1","Data",200,10,700,500);
> c1->SetFillColor(42);
> c1->GetFrame()->SetFillColor(21);
> c1->GetFrame()->SetBorderSize(12);
> c1->GetFrame()->SetBorderMode(-1);
>
> TFile *hfile = (TFile*)gROOT->FindObject("daten.root");
> if (hfile) hfile->Close();
> hfile = new TFile("daten.root","RECREATE","DATA");
>
> data = new TH1F("data","These are the data",42,0,1);
>
> data->SetMarkerColor(4);
> data->SetMarkerStyle(20);
>
> gBenchmark->Start("daten");
>
> //Create the points
> const Int_t n = 42;
> Double_t x[n] =
>
{0.458,0.354,0.425,0.374,0.420,0.372,0.378,0.453,0.465,0.498,0.655,0.4,0.615,0.4
80,0.450,0.388,0.570,0.490,0.495,0.656,0.828,0.450,0.430,0.580,0.763,0.526,0.172
,0.619,0.592,0.550,0.180,0.374,0.472,0.430,0.657,0.612,0.320,0.579,0.450,0.581,0
.416,0.830};
> Double_t y[n] =
>
{23.11,22.38,22.13,21.72,22.55,22.26,22.58,23.17,23.33,23.71,23.27,22.36,23.19,2
2.96,22.51,22.65,23.27,23.10,22.83,23.57,24.65,23.17,23.13,23.46,24.47,23.15,20.
17,23.80,24.42,23.51,20.43,23.52,23.11,22.57,23.83,23.69,21.86,23.48,22.83,23.09
,22.57,24.32};
>
> //create the width of errors in x and y direction
> Double_t ex[n] =
>
{0.001,0.001,0.001,0.001,0.001,0.001,0.001,0.001,0.005,0.001,0.001,0.03,0.001,0.
001,0.001,0.001,0.001,0.01,0.001,0.001,0.001,0.01,0.01,0.001,0.001,0.001,0.001,0
.001,0.001,0.01,0.001,0.001,0.001,0.01,0.001,0.001,0.01,0.001,0.01,0.001,0.001,0
.01};
> Double_t ey[n] =
>
{0.46,0.33,0.49,0.22,0.25,0.20,0.37,0.25,0.30,0.25,0.21,0.19,0.25,0.24,0.23,0.2,
0.22,0.2,0.19,0.28,0.54,0.23,0.22,0.23,0.53,0.20,0.18,0.28,0.37,0.25,0.17,0.24,0
.19,0.18,0.23,0.21,0.18,0.22,0.3,0.22,0.2,0.22};
>
> //create the TGraphErrors and draw
>
> gr = new TGraphErrors(n,x,y,ex,ey);
> gr->SetTitle("Data-file");
> gr->SetMarkerColor(4);
> gr->SetMarkerStyle(20);
> gr->Draw("AP");
>
> gBenchmark->Show("daten");
>
> data->SetMarkerColor(0);
> data->SetMarkerStyle(20);
> hfile->Write();
> data->SetMarkerColor(4);
> data->SetMarkerStyle(20);
> c1->Modified();
> }
>
>
>
> Danilo Behnke
>
>
Eddy A.J.M. Offermann
Renaissance Technologies Corp.
Route 25A, East Setauket NY 11733
e-mail: eddy@rentec.com
http://www.rentec.com
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