TestNonCentral.C

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/// \file
/// \ingroup tutorial_roostats
/// \notebook -js
///
/// \macro_image
/// \macro_output
/// \macro_code
///
/// \author Lorenzo Moneta

using namespace RooFit;
void TestNonCentral(){

   RooWorkspace w("w");
   // k <2, must use sum
   w.factory("NonCentralChiSquare::nc(x[0,50],k[1.99,0,5],lambda[5])");
   // kk > 2 can use bessel
   w.factory("NonCentralChiSquare::ncc(x,kk[2.01,0,5],lambda)");
   // kk > 2, force sum
   w.factory("NonCentralChiSquare::nccc(x,kk,lambda)");
   ((RooNonCentralChiSquare*)w.pdf("nccc"))->SetForceSum(true);

   // a normal "central" chi-square for comparison when lambda->0
   w.factory("ChiSquarePdf::cs(x,k)");

   //w.var("kk")->setVal(4.); // test a large kk

   RooDataSet* ncdata = w.pdf("nc")->generate(*w.var("x"),100);
   RooDataSet* csdata = w.pdf("cs")->generate(*w.var("x"),100);
   RooPlot* plot = w.var("x")->frame();
   ncdata->plotOn(plot,MarkerColor(kRed));
   csdata->plotOn(plot,MarkerColor(kBlue));
   w.pdf("nc")->plotOn(plot,LineColor(kRed));
   w.pdf("ncc")->plotOn(plot,LineColor(kGreen));
   w.pdf("nccc")->plotOn(plot,LineColor(kYellow),LineStyle(kDashed));
   w.pdf("cs")->plotOn(plot,LineColor(kBlue),LineStyle(kDotted));
   plot->Draw();

}