Dear rooters,
I got a strange problem trying to manipulate histograms that I got from graphs. Initially, I was trying to integrate the resulting histogram b/n some limits (the whole reason I needed this), and I was getting 0 as a result all the time.
Then I decided to check what is going on by eye, but the pad where I draw it comes up empty, although axes seem to have correct ranges.
Here is a simple example of what I am doing.
// C++ files
#include<iostream>
using namespace std;
// ROOT files
#include "TROOT.h"
#include "TCanvas.h"
#include "TGraph.h"
#include "TAxis.h"
#include "TH1.h"
int main()
{
const Int_t npts=10;
TCanvas *c_graph = new TCanvas("c_graph","");
TGraph *g_graph = new TGraph(npts);
g_graph->SetMarkerStyle(22);
g_graph->SetMarkerSize(1.2);
g_graph->SetMarkerColor(kRed);
for(int ctr=1;ctr<=npts;ctr++){
g_graph->SetPoint(ctr,ctr,ctr*ctr-ctr);
}
c_graph->Divide(1,2);
c_graph->cd(1); g_graph->Draw("APl");
c_graph->cd(2); g_graph->GetHistogram()->Draw();
c_graph->Print("graph_test.png");
}
Pad #2 is empty.
Could anybody help me with this? If you can directly help me with the problem of integrating graph between some x-values, it’ll be even better.
Slava