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Reference Guide
DynamicSlice.C File Reference

Detailed Description

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Show the slice of a TH2 following the mouse position.

// Create a new canvas.
TCanvas* c1 = new TCanvas("c1","Dynamic Slice Example", 10, 10, 700, 500);
//create a 2-d histogram, fill and draw it
TH2F *hpxpy = new TH2F("hpxpy", "py vs px", 40,-4,4, 40,-4,4);
Double_t px,py;
for (Int_t i = 0; i < 50000; i++) {
//Add a TExec object to the canvas
c1->AddExec("dynamic", "DynamicExec()");
void DynamicExec()
// Example of function called when a mouse event occurs in a pad.
// When moving the mouse in the canvas, a second canvas shows the
// projection along X of the bin corresponding to the Y position
// of the mouse. The resulting histogram is fitted with a gaussian.
// A "dynamic" line shows the current bin position in Y.
// This more elaborated example can be used as a starting point
// to develop more powerful interactive applications exploiting Cling
// as a development engine.
static int pyold = 0;
float uxmin = gPad->GetUxmin();
float uxmax = gPad->GetUxmax();
int pxmin = gPad->XtoAbsPixel(uxmin);
int pxmax = gPad->XtoAbsPixel(uxmax);
int px = gPad->GetEventX();
int py = gPad->GetEventY();
TObject *select = gPad->GetSelected();
if (pyold) {
// erase line at old position
gVirtualX->DrawLine(pxmin, pyold, pxmax, pyold);
pyold = 0;
if(!select || !select->InheritsFrom(TH2::Class()))
TH2 *h = (TH2*)select;
// draw a line at current position
gVirtualX->DrawLine(pxmin, py, pxmax, py);
pyold = py;
Float_t upy = gPad->AbsPixeltoY(py);
Float_t y = gPad->PadtoY(upy);
//create or set the new canvas c2
TVirtualPad *padsav = gPad;
TCanvas *c2 = (TCanvas*)gROOT->GetListOfCanvases()->FindObject("c2");
if(c2) delete c2->GetPrimitive("Projection");
else c2 = new TCanvas("c2","Projection Canvas",710,10,700,500);
//draw slice corresponding to mouse position
Int_t biny = h->GetYaxis()->FindBin(y);
TH1D *hp = h->ProjectionX("",biny,biny);
hp->SetTitle(TString::Format("Projection of biny=%d",biny));
#define h(i)
Definition: RSha256.hxx:106
int Int_t
Definition: RtypesCore.h:45
float Float_t
Definition: RtypesCore.h:57
double Double_t
Definition: RtypesCore.h:59
const Bool_t kTRUE
Definition: RtypesCore.h:100
@ kRed
Definition: Rtypes.h:66
#define gROOT
Definition: TROOT.h:404
R__EXTERN TRandom * gRandom
Definition: TRandom.h:62
#define gPad
Definition: TVirtualPad.h:288
#define gVirtualX
Definition: TVirtualX.h:338
virtual void SetFillColor(Color_t fcolor)
Set the fill area color.
Definition: TAttFill.h:37
virtual void SetLineWidth(Width_t lwidth)
Set the line width.
Definition: TAttLine.h:43
virtual void SetLineColor(Color_t lcolor)
Set the line color.
Definition: TAttLine.h:40
The Canvas class.
Definition: TCanvas.h:23
1-D histogram with a double per channel (see TH1 documentation)}
Definition: TH1.h:620
void SetTitle(const char *title) override
Change (i.e.
Definition: TH1.cxx:6700
virtual TFitResultPtr Fit(const char *formula, Option_t *option="", Option_t *goption="", Double_t xmin=0, Double_t xmax=0)
Fit histogram with function fname.
Definition: TH1.cxx:3894
void Draw(Option_t *option="") override
Draw this histogram with options.
Definition: TH1.cxx:3060
virtual TF1 * GetFunction(const char *name) const
Return pointer to function with name.
Definition: TH1.cxx:8918
void SetName(const char *name) override
Change the name of this histogram.
Definition: TH1.cxx:8827
virtual void SetStats(Bool_t stats=kTRUE)
Set statistics option on/off.
Definition: TH1.cxx:8857
2-D histogram with a float per channel (see TH1 documentation)}
Definition: TH2.h:257
Service class for 2-D histogram classes.
Definition: TH2.h:30
Int_t Fill(Double_t) override
Invalid Fill method.
Definition: TH2.cxx:347
static TClass * Class()
Mother of all ROOT objects.
Definition: TObject.h:41
virtual Bool_t InheritsFrom(const char *classname) const
Returns kTRUE if object inherits from class "classname".
Definition: TObject.cxx:526
virtual void Rannor(Float_t &a, Float_t &b)
Return 2 numbers distributed following a gaussian with mean=0 and sigma=1.
Definition: TRandom.cxx:500
static TString Format(const char *fmt,...)
Static method which formats a string using a printf style format descriptor and return a TString.
Definition: TString.cxx:2345
TVirtualPad is an abstract base class for the Pad and Canvas classes.
Definition: TVirtualPad.h:51
virtual TVirtualPad * cd(Int_t subpadnumber=0)=0
Double_t y[n]
Definition: legend1.C:17
return c1
Definition: legend1.C:41
return c2
Definition: legend2.C:14
Rene Brun, Sergey Linev

Definition in file DynamicSlice.C.