Color Graphics Macro

ROOT
1

Goodmorning, i’m just starting to use root…i need a macro to paint 2D graphics by a color gradient, like this macro:

{
   TCanvas *c1 = new TCanvas("c1","c1",600,600);
   c1->Divide(1,2);
   TH2F *hcol23 = new TH2F("hcol2","Option COLZ example ",40,-4,4,40,-20,20);
   TH2F *hcol24 = new TH2F("hcol2","Option COLZ1 example ",40,-4,4,40,-20,20);
   Float_t px, py;
   for (Int_t i = 0; i < 25000; i++) {
      gRandom->Rannor(px,py);
      hcol23->Fill(px,5*py);
      hcol24->Fill(px,5*py);
   }
   hcol23->Fill(0.,0.,-200.);
   hcol24->Fill(0.,0.,-200.);
   gStyle->SetPalette(kBird);
   c1->cd(1); hcol23->Draw("COLZ");
   c1->cd(2); hcol24->Draw("COLZ1");
   return c1;
}

But in my case, the macro must not generate the numbers, but it must open a data file, can somebody help me to write it please?

2

Your “data file” is what?

3

Hi pepe and thanks! i mean to open a file with 2 culomns, in first culomn there are x-coordinates and in second culomn y-coordinates.

Something like this:

x	y
1	2
2	4
3	6
4	8
4 
{
  TGraph *g1 = new TGraph("file_1.txt");
  TGraph *g2 = new TGraph("file_2.txt");
  
  TCanvas *c = new TCanvas("c","c");
  c->Divide(1, 2);
  c->cd(1); g1->Draw("ALP");
  c->cd(2); g2->Draw("ALP");
  c->cd(0);
}
5

Hi pepe, thanks…but…maybe this is not the kind of graphic that i want…i want a color graph like this:

1788×1116

I tried to combine your code with other codes, and i wrote this:

   
   
   TH2F *hcol23 = new TH2F("hcol2","Option COLZ example ",40,-4,4,40,-20,20);
   TH2F *hcol24 = new TH2F("hcol2","Option COLZ1 example ",40,-4,4,40,-20,20);
   TGraph *c1 = new TGraph("file_1.txt");
  TGraph *c2 = new TGraph("file_2.txt");
    TCanvas *c = new TCanvas("c","c");
   hcol23->Fill(0.,0.,-200.);
   hcol24->Fill(0.,0.,-200.);
   gStyle->SetPalette(52);
   hcol23->Draw("COLZ");
    hcol24->Draw("COLZ1");
   return c1;
}

but this is the result:


…it doen’t paint all the point of the file!

6 
{
  TTree *t1 = new TTree("t1", "tree 1");
  t1->ReadFile("file_1.txt", "x/D:y");
  
  TTree *t2 = new TTree("t2", "tree 2");
  t2->ReadFile("file_2.txt", "x/D:y");
  
  TCanvas *c = new TCanvas("c","c");
  c->Divide(1, 2);
  c->cd(1); t1->Draw("y:x", "", "COLZ");
  c->cd(2); t2->Draw("y:x", "", "COLZ");
  c->cd(0);
}
7

Thank you! other question please…if i wanna open a corsika file, can i just change the name of the data file, or do i need other macro?

8

you’ll need to talk to corsikans.

9

Ok thank you! now i’m just making some prof…next days i will start to use root for graduation thesis, i hope you will help me in the future too

10

ROOT primer
ROOT documentation

11

Thanks for your help pepe