Logo ROOT   6.12/07
Reference Guide
DynamicSlice.C File Reference

Detailed Description

View in nbviewer Open in SWAN Show the slice of a TH2 following the mouse position.

pict1_DynamicSlice.C.png
{
// 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);
hpxpy->SetStats(0);
Double_t px,py;
for (Int_t i = 0; i < 50000; i++) {
gRandom->Rannor(px,py);
hpxpy->Fill(px,py);
}
hpxpy->Draw("col");
//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.
TObject *select = gPad->GetSelected();
if(!select) return;
if (!select->InheritsFrom(TH2::Class())) {gPad->SetUniqueID(0); return;}
TH2 *h = (TH2*)select;
gPad->GetCanvas()->FeedbackMode(kTRUE);
//erase old position and draw a line at current position
int pyold = gPad->GetUniqueID();
int px = gPad->GetEventX();
int py = gPad->GetEventY();
float uxmin = gPad->GetUxmin();
float uxmax = gPad->GetUxmax();
int pxmin = gPad->XtoAbsPixel(uxmin);
int pxmax = gPad->XtoAbsPixel(uxmax);
if(pyold) gVirtualX->DrawLine(pxmin,pyold,pxmax,pyold);
gVirtualX->DrawLine(pxmin,py,pxmax,py);
gPad->SetUniqueID(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);
c2->SetGrid();
c2->cd();
//draw slice corresponding to mouse position
Int_t biny = h->GetYaxis()->FindBin(y);
TH1D *hp = h->ProjectionX("",biny,biny);
hp->SetFillColor(38);
char title[80];
sprintf(title,"Projection of biny=%d",biny);
hp->SetName("Projection");
hp->SetTitle(title);
hp->Fit("gaus","ql");
hp->GetFunction("gaus")->SetLineColor(kRed);
hp->GetFunction("gaus")->SetLineWidth(6);
c2->Update();
padsav->cd();
}
Author
Rene Brun

Definition in file DynamicSlice.C.