Author: Lorenzo Moneta
This notebook tutorial was automatically generated with ROOTBOOK-izer from the macro found in the ROOT repository on Monday, May 29, 2023 at 09:33 AM.
using namespace RooFit;
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();
[#1] INFO:InputArguments -- RooNonCentralChiSquare sum being forced [#0] WARNING:Eval -- RooNonCentralChiSquare did not converge: for x=36 k=2.01, lambda=5 fractional error = 0.00108172 either adjust tolerance with SetErrorTolerance(tol) or max_iter with SetMaxIter(max_it)
Info in <TCanvas::MakeDefCanvas>: created default TCanvas with name c1
Draw all canvases
%jsroot on
gROOT->GetListOfCanvases()->Draw()