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Reference Guide
FirstContour.C File Reference

Detailed Description

View in nbviewer Open in SWAN Make a contour plot and get the first contour in a TPolyMarker.

This macro generates a color contour plot by selecting entries from an ntuple file. The TGraph object corresponding to the first contour line is accessed and displayed into a separate canvas.

void FirstContour()
TString dir = gROOT->GetTutorialDir();
if (!gInterpreter->IsLoaded(dir.Data())) gInterpreter->LoadMacro(dir.Data());
TFile *file = (TFile*)gROOT->ProcessLineFast("hsimple(1)");
if (!file) return;
TTree *ntuple = (TTree*)file->Get("ntuple");
TCanvas *c1 = new TCanvas("c1","Contours",10,10,800,600);
ntuple->Draw("py:px","px*px+py*py < 20", "contz,list");
//we must call Update to force the canvas to be painted. When
//painting the contour plot, the list of contours is generated
//and a reference to it added to the Root list of special objects
TCanvas *c2 = new TCanvas("c2","First contour",100,100,800,600);
TObjArray *contours =
if (!contours) return;
TList *lcontour1 = (TList*)contours->At(0);
if (!lcontour1) return;
TGraph *gc1 = (TGraph*)lcontour1->First();
if (!gc1) return;
if (gc1->GetN() < 10) return;
//We make a TCutG object with the array obtained from this graph
TCutG *cutg = new TCutG("cutg",gc1->GetN(),gc1->GetX(),gc1->GetY());
//We create a polymarker object with npmax points.
const Int_t npmax = 50000;
TPolyMarker *pm = new TPolyMarker(npmax);
Int_t np = 0;
while(1) {
Double_t x = -4 +8*gRandom->Rndm();
Double_t y = -4 +8*gRandom->Rndm();
if (cutg->IsInside(x,y)) {
if (np == npmax) break;
int Int_t
Definition: RtypesCore.h:45
double Double_t
Definition: RtypesCore.h:59
Option_t Option_t TPoint TPoint const char GetTextMagnitude GetFillStyle GetLineColor GetLineWidth GetMarkerStyle GetTextAlign GetTextColor GetTextSize void char Point_t Rectangle_t WindowAttributes_t Float_t Float_t Float_t Int_t Int_t UInt_t UInt_t Rectangle_t Int_t Int_t Window_t TString Int_t GCValues_t GetPrimarySelectionOwner GetDisplay GetScreen GetColormap GetNativeEvent const char const char dpyName wid window const char font_name cursor keysym reg const char only_if_exist regb h Point_t np
#define gInterpreter
Definition: TInterpreter.h:564
#define gROOT
Definition: TROOT.h:404
R__EXTERN TRandom * gRandom
Definition: TRandom.h:62
virtual void SetMarkerStyle(Style_t mstyle=1)
Set the marker style.
Definition: TAttMarker.h:40
The Canvas class.
Definition: TCanvas.h:23
Graphical cut class.
Definition: TCutG.h:20
A ROOT file is a suite of consecutive data records (TKey instances) with a well defined format.
Definition: TFile.h:54
A TGraph is an object made of two arrays X and Y with npoints each.
Definition: TGraph.h:41
virtual Int_t IsInside(Double_t x, Double_t y) const
Return 1 if the point (x,y) is inside the polygon defined by the graph vertices 0 otherwise.
Definition: TGraph.cxx:1820
Double_t * GetY() const
Definition: TGraph.h:134
Int_t GetN() const
Definition: TGraph.h:126
Double_t * GetX() const
Definition: TGraph.h:133
void Draw(Option_t *chopt="") override
Draw this graph with its current attributes.
Definition: TGraph.cxx:806
A doubly linked list.
Definition: TList.h:38
TObject * First() const override
Return the first object in the list. Returns 0 when list is empty.
Definition: TList.cxx:659
An array of TObjects.
Definition: TObjArray.h:31
TObject * At(Int_t idx) const override
Definition: TObjArray.h:164
A PolyMarker is defined by an array on N points in a 2-D space.
Definition: TPolyMarker.h:31
void Draw(Option_t *option="") override
virtual void SetPoint(Int_t point, Double_t x, Double_t y)
Set point number n.
Double_t Rndm() override
Machine independent random number generator.
Definition: TRandom.cxx:552
Basic string class.
Definition: TString.h:136
const char * Data() const
Definition: TString.h:369
TString & ReplaceAll(const TString &s1, const TString &s2)
Definition: TString.h:692
TString & Append(const char *cs)
Definition: TString.h:564
A TTree represents a columnar dataset.
Definition: TTree.h:79
void Draw(Option_t *opt) override
Default Draw method for all objects.
Definition: TTree.h:428
Double_t y[n]
Definition: legend1.C:17
return c1
Definition: legend1.C:41
Double_t x[n]
Definition: legend1.C:17
return c2
Definition: legend2.C:14
Definition: file.py:1
Rene Brun

Definition in file FirstContour.C.