Using ROOT C++ into a C++ code

ROOT
1

Hi everyone,

I want to use ROOT into a C++ code to plot the data generated by C++.

I use this code:

#include <iostream> 
#include <iomanip>

// Root
#include "TAxis.h"
#include "TGraph.h"
#include "TMultiGraph.h"
#include "TCanvas.h"
#include "TApplication.h"
#include "TStyle.h"
#include "TPad.h"
#include "TROOT.h"
#include "TColor.h"
#include "TFrame.h"
#include "TVirtualPad.h"

using namespace std; 

int main() { 
  TCanvas *c1 = new TCanvas("c1","A Simple Graph Example",200,10,700,500); 	
    c1->SetFillColor(42);
   c1->SetGrid();

   const int n = 20;
   double x[n], y[n];
   for (int i=0;i<n;i++) {
     x[i] = i;
     y[i] = 2*i;
     cout<<setprecision(7)<<x[i]<<"\t"<<y[i]<<endl;
    }
 
  TGraph *gr = new TGraph(n,x,y);
   gr->SetLineColor(2);
   gr->SetLineWidth(4);
   gr->SetMarkerColor(4);
   gr->SetMarkerStyle(21);
   gr->SetTitle("a simple graph");
   gr->GetXaxis()->SetTitle("X title");
   gr->GetYaxis()->SetTitle("Y title");
   gr->Draw("ACP");
 
 c1->Update();
 
c1->Modified();

  return 0; 
}

I am compiling in this way:

g++ -c ROOT-CPP.cpp -o root.o -I/usr/local/root/include/
g++ -g root.o -o  root.out `/usr/local/root/bin/root-config --libs`

where ROOT-CPP.cpp is the C++ code source and I installed ROOT in /usr/local/root. The compilation is successful, but when I try to run root.out, it do not generate the graphic window with TCanvas.

Any idea??

Thanks in advance;

Manuel

2

Hi Manuel,

I’m not an expert, but it seems you want a stand alone gui. There is a example of this at http://root.cern.ch/root/html/tutorials/gui/guitest.C.html. It is unfortunately large amount of code, but the very end of it is what you’re interested in.

[code]void guitest()
{
new TestMainFrame(gClient->GetRoot(), 400, 220);
}

//---- Main program ------------------------------------------------------------
#ifdef STANDALONE
int main(int argc, char **argv)
{
TApplication theApp(“App”, &argc, argv);

if (gROOT->IsBatch()) {
fprintf(stderr, “%s: cannot run in batch mode\n”, argv[0]);
return 1;
}

guitest();

theApp.Run();

return 0;
}
#endif[/code]

Surge

3

Hi Manuel,

I worked on your program again and got it work.

[code]#include
#include

// Root
#include “TAxis.h”
#include “TGraph.h”
#include “TMultiGraph.h”
#include “TCanvas.h”
#include “TApplication.h”
#include “TStyle.h”
#include “TPad.h”
#include “TROOT.h”
#include “TColor.h”
#include “TGFrame.h”
#include “TVirtualPad.h”

using namespace std;

void testing() { //new
TCanvas *c1 = new TCanvas(“c1”,“A Simple Graph Example”,200,10,700,500);
c1->SetFillColor(42);
c1->SetGrid();

const int n = 20;
double x[n], y[n];
for (int i=0;i<n;i++) {
	x[i] = i;
	y[i] = 2*i;
	cout<<setprecision(7)<<x[i]<<"\t"<<y[i]<<endl;
}

TGraph *gr = new TGraph(n,x,y);
gr->SetLineColor(2);
gr->SetLineWidth(4);
gr->SetMarkerColor(4);
gr->SetMarkerStyle(21);
gr->SetTitle("a simple graph");
gr->GetXaxis()->SetTitle("X title");
gr->GetYaxis()->SetTitle("Y title");
gr->Draw("ACP");

c1->Update();
c1->Modified();
c1->Connect("Closed()", "TApplication", gApplication, "Terminate()"); //new

}

int main(int argc, char **argv)
{
// all new
TApplication theApp(“App”, &argc, argv);
if (gROOT->IsBatch()) {
fprintf(stderr, “%s: cannot run in batch mode\n”, argv[0]);
return 1;
}
testing();
theApp.Run();
return 0;
}[/code]

I complied by making a Makefile which just had

[code]R_LDFLAGS = root-config --ldflags
R_LIBS = root-config --libs
R_CFLAGS = root-config --cflags
R_ALL = $(R_LADFLAGS) $(R_LIBS) $(R_CFLAGS)

testing: testing.C
g++ -Wall -fPIC $(R_ALL) -c -o testing.o testing.C
g++ -ansi -W -Wall $(R_ALL) -lGui testing.o -o testing
[/code]

I know on the Makefile I went a bit overkill with which flags were necessary when. However, it worked.

Surge

4

Hi Surge,

Thanks so much for your help.

The code worked very well in my computer.

Thanks,

Manuel