How to draw histo BEFORE return?

Newbie
1

My problem is the following: I want to write a macro which draws an histogram for each event in a tree, and let hte user change it from time to time. Here’s the code:


#include "TGraphAsymmErrors.h"
#include "TString.h"
#include "TFile.h"
#include "TH1F.h"
#include "TRandom3.h"
#include "TCanvas.h"
#include "TMath.h"
//#include "Math/SpecFuncMath.h"



#include <iostream>
#include <fstream>
#include <sstream>
#include <cmath>
#include <math.h>


void DrawPads(const char * file_name){
    TH2I * mmq = new TH2I ("mmq","q in pads",35,-2,33,31,0,31);
    

    TFile * inFile =NULL;

    inFile=TFile::Open(file_name);
    if (inFile->IsOpen()){
        cout << "Processing: " << file_name << " ... " << endl;
    }
    else{
        cout<<"failed opening of" << file_name <<endl; 
        return;
    }


    TCanvas *cq = new TCanvas("cq"," charge in pads",1);
    TH2F * opening = new TH2F("histos","_histos",35,-1,34,31,0,31);   
    opening->Draw("");
    

    int padx[70][10];
    int pady[70][10];
    
    int x,y,t;
    int padq[70][10];
    int clusters;
    int multiplicity[70];
    
    TTree *intree = (TTree*)inFile->Get("outtree");
    intree->SetBranchAddress("pad_charge",&padq);
    intree->SetBranchAddress("pad_x",&padx);
    intree->SetBranchAddress("pad_y",&pady);
  
    intree->SetBranchAddress("rob_clusters",&clusters);
    intree->SetBranchAddress("multiplicity",&multiplicity);
    int i=0;
    int control=1;
    while(control){
        cout << "select event. -1 to exit\n"<<endl;
        cin >> i;
        if(i==-1){break;}
        intree->GetEntry(i);
        for(int j=0;j<clusters;j++){
            for(int k=0;k<multiplicity[j];k++){
                mmq->SetBinContent(padx[j][k],pady[j][k],padq[j][k]);
                
            }

        }
    
    

    cq->cd();
    mmq->Draw("colz");
    
    
    }

return ;

}

It all works well except that the histogram is drawn only when the “-1” command is given, that is when the user stops the program (only last event is shown) and return is read.
What am I doing wrong? thank you

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2

After “Draw”, try to add:
gPad->Modified(); gPad->Update(); // make sure it's really (re)drawn

In principle, instead of a simple “cin >> i;”, you need to use some “non-blocking I/O” loop (with “gSystem->ProcessEvents();” inside).

3

thanks, now the problem is that the histograms are “added” at every “i” given as input (entries increasing). How should I pass the “i” input using gSystem->ProcessEvents() ?

4

that the histograms are “added”

How are they “added”, can you describe or show what happens that you don’t want?

5

let’s say the first histogram is drawn and has 45 entries, if I then draw a second histo with 50 entries, i obtain a histo with 95 entries, instead I want ONLY the 50 entries of the second histogram.
Anyway I solved this problem (a little bit cumbersomely) by redefining (and thus subscribing) histos in each call of the loop.
I hope I made myself clear, please let me know…

6

Right before (or after) “GetEntry”, add: mmq->Reset("M");

7

That’s surprising - SetBinContent() should replace whatever has bin in that bin before.

Ah right - there’s an if, so indeed, some bins will keep their values from the previous TTree entry. What @Wile_E_Coyote says! :slight_smile:

8

Thanks. Now everything works fine.

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