TGraph Point Label

ROOT
1

Hi Everybody,
I wanted to know if it is possible in TGraph to show a label near a point with the indication of its quote. If anybody can help me I thank him a lot!
Bye

Pietro

2

Assuming a TGraph* gr object, you can add an annotation object ,eg TText, TLatex, TPaveLabel, etc corresponding to a point in the graph with something like:

TLatex *latex = new TLatex(gr->GetX()[5], gr->GetY()[5],"my annotation"); gr->GetListOfFunctions()->Add(latex); gr->Draw("alp");
It writes an annotation (left adjusted) at the 6-th point of the graph.
You can set the normal graphics attributes for the annotation, eg

latex->SetTextSize(0.07); latex->SetTextColor(kRed);
When drawing the graph, the annotation (or annotations) will be automatically drawn.
If you write the graph to a file, the annotation(s) will also be written.

Rene

3

Thank you very much!

Pietro

4

the line

graf->GetListOfFunctions()->Add(latex);

give me an error

Error: illegal pointer to class object GetListOfFunctions() 0x0 14 graph.C:145:
*** Interpreter error recovered ***

How can I manage to solve the problem?

Thank you

Pietro

5

Could you send the shortest possible running script reproducing the problem? In case you run with an old version, upgrade your version first.

Rene

6

g[i] is an int array
c[i] is a TCanvas* array
pp is a TCanvas*
x and y are double arrays

[code]for(int i=0;i<6;i++){
if(g[i]<0)continue;
pp=c[i];
pp->cd();

TGraph *graf = new TGraph();
int aus=0;
for(int j=g[i];j<N;j++){
	double div, actq, usl;
	int aus2=g[i];
	int att=0;
	if(aus==0){while(1>0){div=y[aus2];
		   	      if(fabs(div)>.00000001)break;
			      aus2--;
			      att++;
			      }
		   }
	if(att!=0 && j==g[i]){actq=(y[aus2]/div);}
	else{actq=(y[j]/div);}
	if(fabs(actq)<.0000000001)graf->GetPoint(aus-1,usl,actq);
	graf->SetPoint(aus,x[j],actq);
	aus++;
	}
TLatex *latex = new TLatex(graf->GetX()[4],graf->GetY()[4],"pippo");
graf->GetListOfFunctions()->Add(latex);[/code]

I’m using ROOT Version 5.12/00 July 06.
Thank You

Bye
Pietro[/code]

7

Replace the line

TGraph *graf = new TGraph(); by

TGraph *graf = new TGraph(0); or better

TGraph *graf = new TGraph(N);
Rene

8

Thanks

Pietro

9

This is valid for a single point. But if I want to do it for multiple points in a loop, then how to do it?

10 
void graphtext2() {
   TCanvas *c = new TCanvas("c","A Simple Graph Example with Text",700,500);
   c->SetGrid();
   const Int_t n = 10;
   TGraph *gr = new TGraph(n);
   gr->SetTitle("A Simple Graph Example with Text");
   gr->SetMarkerStyle(20);
   TExec *ex = new TExec("ex","DrawText();");

   gr->GetListOfFunctions()->Add(ex);

   Double_t x, y;
   for (Int_t i=0;i<n;i++) {
      x = i*0.1;
      y = 10*sin(x+0.2);
      gr->SetPoint(i,x,y);

   }

   gr->Draw("ALP");
}


void DrawText()
{
   Int_t i,n;
   Double_t x,y;
   TLatex *l;

   TGraph *g = (TGraph*)gPad->GetListOfPrimitives()->FindObject("Graph");
   n = g->GetN();
   for (i=1; i<n; i++) {
      g->GetPoint(i,x,y);
      l = new TLatex(x,y+0.2,Form("%4.2f",y));
      l->SetTextSize(0.025);
      l->SetTextFont(42);
      l->SetTextAlign(21);
      l->Paint();
   }
}
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11

Please don’t reply to old topics (17 years old!)

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