Macro to test interpolation function Approx
Author: Christian Stratowa, Vienna, Austria.
This notebook tutorial was automatically generated with ROOTBOOK-izer from the macro found in the ROOT repository on Wednesday, April 17, 2024 at 11:11 AM.
TCanvas *vC1;
TGraph *grxy, *grin, *grout;
Definition of a helper function:
%%cpp -d
void DrawSmooth(Int_t pad, const char *title, const char *xt, const char *yt)
{
vC1->cd(pad);
TH1F *vFrame = gPad->DrawFrame(0,0,15,150);
vFrame->SetTitle(title);
vFrame->SetTitleSize(0.2);
vFrame->SetXTitle(xt);
vFrame->SetYTitle(yt);
grxy->SetMarkerColor(kBlue);
grxy->SetMarkerStyle(21);
grxy->SetMarkerSize(0.5);
grxy->Draw("P");
grin->SetMarkerColor(kRed);
grin->SetMarkerStyle(5);
grin->SetMarkerSize(0.7);
grin->Draw("P");
grout->DrawClone("LP");
}
Test data (square)
Int_t n = 11;
Double_t x[] = {1,2,3,4,5,6,6,6,8,9,10};
Double_t y[] = {1,4,9,16,25,25,36,49,64,81,100};
grxy = new TGraph(n,x,y);
X values, for which y values should be interpolated
Int_t nout = 14;
Double_t xout[] =
{1.2,1.7,2.5,3.2,4.4,5.2,5.7,6.5,7.6,8.3,9.7,10.4,11.3,13};
Create Canvas
vC1 = new TCanvas("vC1","square",200,10,700,700);
vC1->Divide(2,2);
Initialize graph with data
grin = new TGraph(n,x,y);
Interpolate at equidistant points (use mean for tied x-values)
TGraphSmooth *gs = new TGraphSmooth("normal");
grout = gs->Approx(grin,"linear");
DrawSmooth(1,"Approx: ties = mean","X-axis","Y-axis");
Re-initialize graph with data (since graph points were set to unique vales)
grin = new TGraph(n,x,y);
Interpolate at given points xout
grout = gs->Approx(grin,"linear", 14, xout, 0, 130);
DrawSmooth(2,"Approx: ties = mean","","");
Print output variables for given values xout
Int_t vNout = grout->GetN();
Double_t vXout, vYout;
for (Int_t k=0;k<vNout;k++) {
grout->GetPoint(k, vXout, vYout);
cout << "k= " << k << " vXout[k]= " << vXout
<< " vYout[k]= " << vYout << endl;
}
k= 0 vXout[k]= 1.2 vYout[k]= 1.6 k= 1 vXout[k]= 1.7 vYout[k]= 3.1 k= 2 vXout[k]= 2.5 vYout[k]= 6.5 k= 3 vXout[k]= 3.2 vYout[k]= 10.4 k= 4 vXout[k]= 4.4 vYout[k]= 19.6 k= 5 vXout[k]= 5.2 vYout[k]= 27.3333 k= 6 vXout[k]= 5.7 vYout[k]= 33.1667 k= 7 vXout[k]= 6.5 vYout[k]= 43.5 k= 8 vXout[k]= 7.6 vYout[k]= 58.5333 k= 9 vXout[k]= 8.3 vYout[k]= 69.1 k= 10 vXout[k]= 9.7 vYout[k]= 94.3 k= 11 vXout[k]= 10.4 vYout[k]= 130 k= 12 vXout[k]= 11.3 vYout[k]= 130 k= 13 vXout[k]= 13 vYout[k]= 130
Re-initialize graph with data
grin = new TGraph(n,x,y);
Interpolate at equidistant points (use min for tied x-values) grout = gs->Approx(grin,"linear", 50, 0, 0, 0, 1, 0, "min");
grout = gs->Approx(grin,"constant", 50, 0, 0, 0, 1, 0.5, "min");
DrawSmooth(3,"Approx: ties = min","","");
Re-initialize graph with data
grin = new TGraph(n,x,y);
Interpolate at equidistant points (use max for tied x-values)
grout = gs->Approx(grin,"linear", 14, xout, 0, 0, 2, 0, "max");
DrawSmooth(4,"Approx: ties = max","","");
Cleanup
delete gs;
Draw all canvases
%jsroot on
gROOT->GetListOfCanvases()->Draw()