How to draw all entries in TMatrix

Newbie
1

Hi, I am trying to draw 45 entries in Tmatrix together in one canvas. I am using the following code:

  TFile* outFile = new TFile("myrootfile.root");
  TTree* outTree = (TTree*)outFile->Get("out_tree");
  outTree->Print(); // print tree to be sure of its content
  TMatrixD *matrix1 = nullptr;
  outTree->SetBranchAddress("myBranch", &matrix1);
  Long64_t events = outTree->GetEntries();
  cout<<"Number of events : "<<events<<endl;

 for(int i=0; i<events; i++){
	  outTree->GetEntry(i);
	  TH2D *h = new TH2D(*matrix1);
	  h->SetNameTitle("h", "matrix;x axis;y axis");
	  h->Draw("colz");
	  h->SetStats(0);
  
  }

But I am only getting one entry (event) instead of all of them on the same canvas. Is it possible?

Thank you!

2

If you recreate the same TH2D and call Draw() inside the loop, then you’ll see only the last one…
EDIT: Sorry, I overlooked at your code. Can you provide the root file?

3

No problem. Here it is.
outputFile.root (371.7 KB)

EDIT: can I maybe create something that draws events when I call them in the command line?
For example: typing “1” draws event number 1 and so on. So I don’t have to edit the code every time.

4

If you try this:

   for (int i=0; i<events; i++) {
      cout<<"Reading Event "<<i<<endl;
      outTree->GetEntry(i);
      TH2D *h = new TH2D(*matrix1);
      h->SetNameTitle("h", "matrix;x axis;y axis");
      h->Draw("colz");
      h->SetStats(0);
      gPad->Modified();
      gPad->Update();
      gSystem->Sleep(1000);
   }

You’ll see the events one after the other.
So you can create a function with parameters, like for example:

#include "TFile.h"
#include "TTree.h"
#include "TMatrixD.h"

void print_info(const char *file_name = "outputFile.root", const char *tree_name = "out_tree")
{
   TFile* outFile = TFile::Open(file_name);
   TTree* outTree = (TTree*)outFile->Get(tree_name);
   outTree->Print(); // print tree to be sure of its content
   outFile->Close();
   delete outFile;
}

void read_output(Int_t entry = 0, const char *file_name = "outputFile.root", const char *branch_name = "PadCharge",
                 const char *tree_name = "out_tree")
{
   TFile* outFile = TFile::Open(file_name);
   TTree* outTree = (TTree*)outFile->Get(tree_name);
   TMatrixD *matrix1 = nullptr;
   outTree->SetBranchAddress(branch_name, &matrix1);
   outTree->GetEntry(entry);
   TH2D *h = new TH2D(*matrix1);
   h->SetDirectory(nullptr);
   h->SetNameTitle("h", "matrix;x axis;y axis");
   h->Draw("colz");
   h->SetStats(0);
   gPad->Modified();
   gPad->Update();
   outFile->Close();
   delete outFile;
}

And then you can use it that way:

C:\Users\bellenot\rootdev\Forum>root -l
root [0] .L read_output.C
root [1] print_info()
******************************************************************************
*Tree    :out_tree  : out_tree                                               *
*Entries :       46 : Total =         1536133 bytes  File  Size =     374839 *
*        :          : Tree compression factor =   4.10                       *
******************************************************************************
*Br    0 :PadCharge : TMatrixD                                               *
*Entries :       46 : Total  Size=     759250 bytes  File Size  =     145942 *
*Baskets :       16 : Basket Size=      64000 bytes  Compression=   5.20     *
*............................................................................*
*Br    1 :PadTime   : TMatrixD                                               *
*Entries :       46 : Total  Size=     759212 bytes  File Size  =     225817 *
*Baskets :       16 : Basket Size=      64000 bytes  Compression=   3.36     *
*............................................................................*
*Br    2 :SilCharge : TVectorD                                               *
*Entries :       46 : Total  Size=       8634 bytes  File Size  =       1393 *
*Baskets :        1 : Basket Size=      64000 bytes  Compression=   5.84     *
*............................................................................*
*Br    3 :SilID     : TVectorD                                               *
*Entries :       46 : Total  Size=       8618 bytes  File Size  =        691 *
*Baskets :        1 : Basket Size=      64000 bytes  Compression=  11.77     *
*............................................................................*
root [2] read_output(2)
Info in <TCanvas::MakeDefCanvas>:  created default TCanvas with name c1
root [3]
1 Like
5

Thanks. And is it also possible to show all in one canvas. Maybe read_output(all) or so?

6

Sure, but then you have to divide your canvas

7

Yes, dividing is one way but is it possible to see all events together on one histogram?

8

You mean add them, or superimpose?

9

Indeed superimpose is what I meant.

10

h->Draw("colz same");

1 Like
11

Great, thanks!