Loading data file to make a plot of multiple y values for a single x values

General Chat
1

Hi
I have 4 .dat files each with 2 arrays. In each files, First one array corresponds to Voltage and second one correspond to Gain at different conditions. I want to make a plot of Gain vs. Voltage at one graph (not individually).
Can any one help me out with a code?
I wrote the following one but it doesnt work.

{

TCanvas *c1= new TCanvas ("c1", "", 700, 600);

TMultiGraph *mg= new TMultiGraph ();


TGraph gr0 ("CH0.dat", "%lg %lg");
gr0.SetMarkerStyle (kFullCircle);	
gr0.SetMarkerColor (kRed);	
gr0.Draw ("");

TGraph gr1 ("CH1.dat", "%lg %lg");
gr1.SetMarkerStyle (kFullCircle);
gr1.SetMarkerColor (kBlue);
gr1.Draw("");

TGraph gr2 ("CH2.dat", "%lg %lg");
gr2.SetMarkerStyle (kMultiply);
gr2.SetMarkerColor (kBlack);
gr2.Draw("");

TGraph gr3 ("CH3.dat", "%lg %lg");
gr3.SetMarkerStyle (kStar);
gr3.SetMarkerColor (kBlack);
gr3.Draw ("");

mg->Add ("gr0");
mg->Add ("gr1");
mg->Add ("gr2");
mg->Add ("gr3");

mg->Draw("");

}

2

[code]{
TGraph *gr0 = new TGraph (“CH0.dat”, “%lg %lg”);
gr0->SetMarkerStyle (kFullCircle);
gr0->SetMarkerColor (kRed);

TGraph *gr1 = new TGraph (“CH1.dat”, “%lg %lg”);
gr1->SetMarkerStyle (kFullCircle);
gr1->SetMarkerColor (kBlue);

TGraph *gr2 = new TGraph (“CH2.dat”, “%lg %lg”);
gr2->SetMarkerStyle (kMultiply);
gr2->SetMarkerColor (kBlack);

TGraph *gr3 = new TGraph (“CH3.dat”, “%lg %lg”);
gr3->SetMarkerStyle (kStar);
gr3->SetMarkerColor (kBlack);

TMultiGraph *mg = new TMultiGraph();
mg->Add (gr0);
mg->Add (gr1);
mg->Add (gr2);
mg->Add (gr3);

TCanvas *c1 = new TCanvas (“c1”, “”, 700, 600);

mg->Draw(“AP”);
}[/code]

3

Thank you so much. It worked. 8)
However I am not able to set colors of my choice for pol1 fit lines. i used the following code: [code]{
TGraph *gr0 = new TGraph (“CH0.dat”, “%lg %lg”);
gr0->SetMarkerStyle (kFullCircle);
gr0->SetMarkerColor (kRed);
gr0->Fit(“pol1”);
gr0->SetLineColor(kRed);

TGraph *gr1 = new TGraph (“CH1.dat”, “%lg %lg”);
gr1->SetMarkerStyle (kFullCircle);
gr1->SetMarkerColor (kBlue);
gr1->Fit(“pol1”);
gr1->SetLineColor (kBlue);

TGraph *gr2 = new TGraph (“CH2.dat”, “%lg %lg”);
gr2->SetMarkerStyle (kMultiply);
gr2->SetMarkerColor (kBlack);
gr2->Fit(“pol1”);
gr2->SetLineColor (kBlack);

TGraph *gr3 = new TGraph (“CH3.dat”, “%lg %lg”);
gr3->SetMarkerStyle (kStar);
gr3->SetMarkerColor (kGreen);
gr3->Fit(“pol1”);
gr3->SetLineColor (kGreen);

TMultiGraph *mg = new TMultiGraph();
mg->SetTitle (“Gain vs. Voltage”);
mg->Add (gr0);
mg->Add (gr1);
mg->Add (gr2);
mg->Add (gr3);

TCanvas *c1 = new TCanvas (“c1”, “”, 700, 600);

mg->Draw(“AP”);
}
[/code]

Also, before whenever I wrote
TGraph *gr0 = new TGraph ()
gr0->Draw ()

an error message used to pop up saying TGraph doesnt belong to POINTER class and I should use Dots (.) instead… But right now its working with Pointers… Could you please explain me why?

4

// ... gr0->GetFunction("pol1")->SetLineColor(kRed); // ... gr1->GetFunction("pol1")->SetLineColor(kBlue); // ... gr2->GetFunction("pol1")->SetLineColor(kBlack); // ... gr3->GetFunction("pol1")->SetLineColor(kGreen); // ...

5

Thank you so much. It worked now.