hist003_TH1_draw.C

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/// \file
/// \ingroup tutorial_hist
/// \notebook
/// Draw a 1D histogram to a canvas.
///
/// \note When using graphics inside a ROOT macro the objects must be created with `new`.
///
/// \macro_image
/// \macro_code
///
/// \date November 2024
/// \author Rene Brun, Giacomo Parolini
 
void hist003_TH1_draw()
{
   // Create and fill the histogram.
   // See hist002_TH1_fillrandom_userfunc.C for more information about this section.
   auto *form1 = new TFormula("form1", "abs(sin(x)/x)");
   double rangeMin = 0.0;
   double rangeMax = 10.0;
   auto *sqroot = new TF1("sqroot", "x*gaus(0) + [3]*form1", rangeMin, rangeMax);
   sqroot->SetLineColor(4);
   sqroot->SetLineWidth(6);
   sqroot->SetParameters(10.0, 4.0, 1.0, 20.0);
 
   int nBins = 200;
   auto *h1d = new TH1D("h1d", "Test random numbers", nBins, rangeMin, rangeMax);
 
   h1d->FillRandom("sqroot", 10000);
 
   // Create a canvas and draw the histogram
   int topX = 200;
   int topY = 10;
   int width = 700;
   int height = 900;
   auto *c1 = new TCanvas("c1", "The FillRandom example", topX, topY, width, height);
 
   // Split the canvas into two sections to plot both the function and the histogram
   // The TPad's constructor accepts the relative coordinates (0 to 1) of the pad's boundaries
   auto *pad1 = new TPad("pad1", "The pad with the function", 0.05, 0.50, 0.95, 0.95);
   auto *pad2 = new TPad("pad2", "The pad with the histogram", 0.05, 0.05, 0.95, 0.45);
 
   // Draw the two pads
   pad1->Draw();
   pad2->Draw();
 
   // Select pad1 to draw the next objects into
   pad1->cd();
   pad1->SetGridx();
   pad1->SetGridy();
   pad1->GetFrame()->SetBorderMode(-1);
   pad1->GetFrame()->SetBorderSize(5);
 
   // Draw the function in pad1
   sqroot->Draw();
   // Add a label to the function.
   // TPaveLabel's constructor accepts the pixel coordinates and the label string.
   auto *lfunction = new TPaveLabel(5, 39, 9.8, 46, "The sqroot function");
   lfunction->Draw();
   c1->Update();
 
   // Select pad2 to draw the next objects into
   pad2->cd();
   pad2->GetFrame()->SetBorderMode(-1);
   pad2->GetFrame()->SetBorderSize(5);
 
   h1d->SetFillColor(45);
   h1d->Draw();
   c1->Update();
}