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Reference Guide
approx.C File Reference

Detailed Description

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Macro to test interpolation function Approx

TCanvas *vC1;
TGraph *grxy, *grin, *grout;
void DrawSmooth(Int_t pad, const char *title, const char *xt, const char *yt)
TH1F *vFrame = gPad->DrawFrame(0,0,15,150);
void approx()
// 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[] =
// Create Canvas
vC1 = new TCanvas("vC1","square",200,10,700,700);
// 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;
// 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;
int Int_t
Definition: RtypesCore.h:45
double Double_t
Definition: RtypesCore.h:59
@ kRed
Definition: Rtypes.h:66
@ kBlue
Definition: Rtypes.h:66
#define gPad
Definition: TVirtualPad.h:288
virtual void SetMarkerColor(Color_t mcolor=1)
Set the marker color.
Definition: TAttMarker.h:38
virtual void SetMarkerStyle(Style_t mstyle=1)
Set the marker style.
Definition: TAttMarker.h:40
virtual void SetMarkerSize(Size_t msize=1)
Set the marker size.
Definition: TAttMarker.h:45
The Canvas class.
Definition: TCanvas.h:23
TVirtualPad * cd(Int_t subpadnumber=0) override
Set current canvas & pad.
Definition: TCanvas.cxx:711
A helper class to smooth TGraph.
Definition: TGraphSmooth.h:36
TGraph * Approx(TGraph *grin, Option_t *option="linear", Int_t nout=50, Double_t *xout=nullptr, Double_t yleft=0, Double_t yright=0, Int_t rule=0, Double_t f=0, Option_t *ties="mean")
Approximate data points.
A TGraph is an object made of two arrays X and Y with npoints each.
Definition: TGraph.h:41
Int_t GetN() const
Definition: TGraph.h:126
void Draw(Option_t *chopt="") override
Draw this graph with its current attributes.
Definition: TGraph.cxx:808
virtual Int_t GetPoint(Int_t i, Double_t &x, Double_t &y) const
Get x and y values for point number i.
Definition: TGraph.cxx:1520
1-D histogram with a float per channel (see TH1 documentation)}
Definition: TH1.h:577
virtual void SetTitleSize(Float_t size=0.02, Option_t *axis="X")
Set the axis' title size.
Definition: Haxis.cxx:365
void SetTitle(const char *title) override
Change (i.e.
Definition: TH1.cxx:6700
virtual void SetXTitle(const char *title)
Definition: TH1.h:415
virtual void SetYTitle(const char *title)
Definition: TH1.h:416
virtual TObject * DrawClone(Option_t *option="") const
Draw a clone of this object in the current selected pad for instance with: gROOT->SetSelectedPad(gPad...
Definition: TObject.cxx:298
void Divide(Int_t nx=1, Int_t ny=1, Float_t xmargin=0.01, Float_t ymargin=0.01, Int_t color=0) override
Automatic pad generation by division.
Definition: TPad.cxx:1153
Double_t y[n]
Definition: legend1.C:17
Double_t x[n]
Definition: legend1.C:17
const Int_t n
Definition: legend1.C:16
Christian Stratowa, Vienna, Austria.

Definition in file approx.C.