graphtext.C

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/// \file
/// \ingroup tutorial_graphs
/// \notebook
/// Draw a graph with text attached to each point.
/// The text is drawn in a TExec function attached to the TGraph,
/// therefore if the a graph's point is
/// moved interactively, the text will be automatically updated.
///
/// \macro_image
/// \macro_code
///
/// \author Olivier Couet

void graphtext() {
   TCanvas *c = new TCanvas("c","A Simple Graph Example with Text",700,500);
   c->SetGrid();

   const Int_t n = 10;
   auto gr = new TGraph(n);
   gr->SetTitle("A Simple Graph Example with Text");
   gr->SetMarkerStyle(20);
   auto 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;

   l.SetTextSize(0.025);
   l.SetTextFont(42);
   l.SetTextAlign(21);
   l.SetTextColor(kBlue);

   auto g = (TGraph*)gPad->GetListOfPrimitives()->FindObject("Graph");
   n = g->GetN();

   for (i=0; i<n; i++) {
      g->GetPoint(i,x,y);
      l.PaintText(x,y+0.2,Form("(%4.2f,%4.2f)",x,y));
   }
}