DrawCopy crashes program

ROOT
1

Hello Rooters,

I am trying to draw several fifferent histograms in a while loop.
Since I modify the original histogram in each iteration I use ‘DrawCopy’ to draw the histograms.
I already did exactly the same with 1-dim histograms and it worked fine but with the 2-dim histograms the program crashes at the ‘DrawCopy’ command (note that eg. ‘Draw’ doesn’t crash the program).
I tried different ideas but nothing helped. Do you have any suggestion what could be the problem?

I should add that I am using VC++6.0 and ROOT 4.0.

Thanks a lot for any reply!
Gerolf

here is the piece of code:

int ichan;
while(ichan<=20) {
sprintf(tmp,“pmt==%d”,ichan);
TCut c1 = tmp;
c->GetCanvas()->cd(ichan);
tree->Draw(“s0:event>>bufhist2”,c1);
TH2F bufhist2 = (TH2F)gPad->GetPrimitive(“bufhist2”);
bufhist2->DrawCopy();
}

2

I cannot reproduce this problem. Could you send a very short script?

Rene

3

Hello Rene,
here is the script that I use!
It crashes at the ‘DrawCopy’ commmand.

Cheers,
Gerolf

int pedestal(TRootEmbeddedCanvas *c)
{
TH2F *h2 = new TH2F(“h2”,“title”,100,0,50,100,0,300);
char line[40];
struct event_t {
int evt;
int pmt;
int gain;
int s0;
int s1;
int s2;
int s3;
int s4;
int s5;
int s6;
};
event_t event;

FILE *fp = fopen(“test2.dat”,“r”);
TFile *f = new TFile(“test.root”,“RECREATE”);
TTree *tree = new TTree(“tree”,“pedestals”);
tree->Branch(“event”,&event.evt,“evt/I:pmt:gain:s0:s1:s2:s3:s4:s5:s6”);
while (fgets(line,40,fp)) {
sscanf(line," %d %d %d,%d,%d,%d,%d,%d,%d,%d\n",&event.evt,&event.pmt,&event.gain,&event.s0,&event.s1,&event.s2,&event.s3,&event.s4,&event.s5,&event.s6);
tree->Fill();
}

while(ichan<=20) {
sprintf(tmp,“pmt==%d”,ichan);
TCut c1 = tmp;
c->GetCanvas()->cd(ichan);
tree->Draw(“s0:event>>h2”,c1);
h2 = (TH2F*)gPad->GetPrimitive(“h2”);
h2->DrawCopy();
ichan++;
}

fclose(fp);
f->Write();
c->GetCanvas()->Modified();
c->GetCanvas()->Update();
c->GetCanvas()->Print(“testgraph.ps)”);
return 0;
}

4

please send the data files

Rene

5

Hello rene,

here is the data file.
I had to change the ending to ‘.txt’ because ‘.dat’ files were not allowed.

cheers,
Gerolf
test2.txt (553 KB)

6

Your script cannot be executed as such. It contains undefined
variables (eg tmp, ichan).
If it crashes when calling DrawCopy, it means that your pointer h2 is null.
ie, 0 events pass the cut.
If you do not find your problem, please send the shortest self-contained script reproducing the problem.

Rene

7

Hello Rene,

we continued trying to find the root of problem and arrived at the following piece of code. With tree->Draw(“s0:event>>h2”,c1,“N”) it works but without …,“N”) it does not work (see code).
Can you please tell us why?

Thanks,
Gerolf

PS.: Code and Data file are attached
PPS.: I hope this time the code is really ‘standalone’

#include
#include
#include
#include <Riostream.h>
#include <TSystem.h>
#include <stdio.h>
#include <TROOT.h>
#include <TRootApplication.h>
#include <TRootEmbeddedCanvas.h>
#include <TH2F.h>
#include <TFile.h>
#include <TCut.h>
#include <TTree.h>
#include <TCanvas.h>
#include <TApplication.h>
#include <TQObject.h>
#include <TVirtualX.h>

int main(int argc, char ** argv)
{

char line[40];

char tmp[70];
int ichan=1;
TH2F *h2 = 0;

struct event_t {
int evt;
int pmt;
int gain;
int s0;
int s1;
int s2;
int s3;
int s4;
int s5;
int s6;
};
event_t event;
//TApplication app(“test”,&argc,argv); // For compiling in Visual C++

TCanvas *c = new TCanvas("Canvas");
FILE *fp = fopen("test2.txt","r"); 
TFile *f = new TFile("test.root","RECREATE"); 
TTree *tree = new TTree("tree","pedestals"); 
tree->Branch("event",&event.evt,"evt/I:pmt:gain:s0:s1:s2:s3:s4:s5:s6"); 

while (fgets(line,40,fp)) { 
	sscanf(line," %d %d %d,%d,%d,%d,%d,%d,%d,%d\n",&event.evt,&event.pmt,&event.gain,&event.s0,&event.s1,&event.s2,&event.s3,&event.s4,&event.s5,&event.s6); 
	tree->Fill(); 
} 
c->GetCanvas()->Divide(2,2);
while(ichan<=4) { 
	sprintf(tmp,"pmt==%d",ichan); 
	TCut c1 = tmp; 
	c->GetCanvas()->cd(ichan); 
	if (h2) {
		delete h2;
		h2=0;
	}

	tree->Draw("s0:event>>h2",c1,"N");		// works  !!!!!!!!
	//tree->Draw("s0:event>>h2",c1);	// doesn't work  !!!!!!!!!

	h2 = (TH2F*)gPad->GetPrimitive("h2");
	gPad->Update();
	if (h2 != (TH2F*)gDirectory->Get("h2")) {
		cout << "Different "  << hex <<
			(int) h2 << " " << (int) (TH2F*)gDirectory->Get("h2") << dec << endl;
	}
	gSystem->Sleep(500);
	gPad->Clear();
	h2->Print();
	h2->DrawCopy();
	gPad->Update();
	ichan++; 
} 
fclose(fp); 

//app.Run(kTRUE); // For compiling in Visual C++
return 0;

}
test2.txt (553 KB)

8

Your macro runs correctly with versions 3.10/07
and the current version 4.00/06.
I get the 4 scatter-plots (one per pad)

TH1.Print Name= h2, Entries= 400, Total sum= 400
TH1.Print Name= h2, Entries= 400, Total sum= 400
TH1.Print Name= h2, Entries= 400, Total sum= 400
TH1.Print Name= h2, Entries= 400, Total sum= 400

Rene