doc/v608/simple_8cxx.html

/*************************************************************************
 * Copyright (C) 1995-2015, Rene Brun and Fons Rademakers.               *
 * All rights reserved.                                                  *
 *                                                                       *
 * For the licensing terms see $ROOTSYS/LICENSE.                         *
 * For the list of contributors see $ROOTSYS/README/CREDITS.             *
 *************************************************************************/
#include "ROOT/THist.hxx"
#include "ROOT/TFit.hxx"
#include "ROOT/TFile.hxx"
void simple() {
  using namespace ROOT;
  // Create a 2D histogram with an X axis with equidistant bins, and a y axis
  // with irregular binning.
  Experimental::TAxisConfig xAxis(100, 0., 1.);
  Experimental::TAxisConfig yAxis({0., 1., 2., 3.,10.});
  Experimental::TH2D histFromVars(xAxis, yAxis);
  // Or the short in-place version:
  // Create a 2D histogram with an X axis with equidistant bins, and a y axis
  // with irregular binning.
  Experimental::TH2D hist({100, 0., 1.}, {{0., 1., 2., 3.,10.}});
  // Fill weight 1. at the coordinate 0.01, 1.02.
  hist.Fill({0.01, 1.02});
  // Fit the histogram.
  Experimental::TFunction<2> func([](const std::array<double,2>& x,
                             const std::array_view<double>& par)
                          { return par[0]*x[0]*x[0] + (par[1]-x[1])*x[1]; });
  Experimental::TFitResult fitResult = Experimental::FitTo(hist, func, {{0., 1.}});
  Experimental::TFilePtr file = Experimental::TFile::Recreate("hist.root");
  file->Write("TheHist", hist);
}