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));
   }
}