Trouble with getting GetChiSquare() function running properly

Newbie
1

Hello I have a code which I simplified down below
My issue stems from the second to last line where if I try to use it
It spits out a long error which I show at the bottom. I’m not sure on where I’m going wrong with using the function.

void fplot()
{
	TH1D* h1 = new TH1D("h1","",10,0,10);
	h1->SetBinContent(1, TMath::Poisson(0.,1));
	h1->SetBinContent(2, TMath::Poisson(0.,2));
	h1->SetBinContent(3, TMath::Poisson(0.,3));
	h1->SetBinContent(4, TMath::Poisson(0.,4));
	h1->SetBinContent(5, TMath::Poisson(0.,5));
	h1->SetBinContent(6, TMath::Poisson(0.,6));
	h1->SetBinContent(7, TMath::Poisson(0.,7));
	h1->SetBinContent(8, TMath::Poisson(0.,8));
	h1->SetBinContent(9, TMath::Poisson(0.,9));
	h1->SetBinContent(10,TMath::Poisson(0.,10));
	
	TF1 *Poisson = new TF1("Poisson", "TMath::Poisson(0.,x)", 0., 10.);
	
	Poisson -> Draw();
	h1 -> Draw("same");
	
	TF1 *fit = h1 -> GetFunction("Poisson");
	double_t chi = fit -> GetChisquare();
	cout << "ChiTest(1)" << chi << endl;
}

==========================================
=============== STACKTRACE ===============
==========================================


================ Thread 0 ================
  C:\build\ws\BUILDTYPE\Debug\LABEL\windows10\V\6-24\root\core\metacling\src\TClingCallbacks.cxx(922): TClingCallbacks::PrintStackTrace()
  libCling!cling::MultiplexInterpreterCallbacks::PrintStackTrace()
  libCling!cling_runtime_internal_throwIfInvalidPointer()
  0xe0edbb6 ??
  0xe0ef037 ??
  libCling!cling::IncrementalExecutor::executeWrapper()
  libCling!cling::Interpreter::RunFunction()
  libCling!cling::Interpreter::EvaluateInternal()
  libCling!cling::Interpreter::process()
  libCling!cling::MetaProcessor::process()
  C:\build\ws\BUILDTYPE\Debug\LABEL\windows10\V\6-24\root\core\metacling\src\TCling.cxx(2427): HandleInterpreterException()
  C:\build\ws\BUILDTYPE\Debug\LABEL\windows10\V\6-24\root\core\metacling\src\TCling.cxx(2587): TCling::ProcessLine()
  C:\build\ws\BUILDTYPE\Debug\LABEL\windows10\V\6-24\root\core\base\src\TApplication.cxx(1472): TApplication::ProcessLine()
  C:\build\ws\BUILDTYPE\Debug\LABEL\windows10\V\6-24\root\core\rint\src\TRint.cxx(751): TRint::ProcessLineNr()
  C:\build\ws\BUILDTYPE\Debug\LABEL\windows10\V\6-24\root\core\rint\src\TRint.cxx(613): TRint::HandleTermInput()
  C:\build\ws\BUILDTYPE\Debug\LABEL\windows10\V\6-24\root\core\winnt\src\TWinNTSystem.cxx(1615): TWinNTSystem::DispatchOneEvent()
  C:\build\ws\BUILDTYPE\Debug\LABEL\windows10\V\6-24\root\core\base\src\TSystem.cxx(405): TSystem::InnerLoop()
  C:\build\ws\BUILDTYPE\Debug\LABEL\windows10\V\6-24\root\core\base\src\TSystem.cxx(355): TSystem::Run()
  C:\build\ws\BUILDTYPE\Debug\LABEL\windows10\V\6-24\root\core\base\src\TApplication.cxx(1624): TApplication::Run()
  C:\build\ws\BUILDTYPE\Debug\LABEL\windows10\V\6-24\root\core\rint\src\TRint.cxx(466): TRint::Run()
  C:\build\ws\BUILDTYPE\Debug\LABEL\windows10\V\6-24\root\main\src\rmain.cxx(32): main()
  d:\agent\_work\4\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl(288): __scrt_common_main_seh()
  KERNEL32!BaseThreadInitThunk()
  ntdll!RtlGetAppContainerNamedObjectPath()
  ntdll!RtlGetAppContainerNamedObjectPath()

================ Thread 1 ================
  ntdll!NtDelayExecution()
  KERNELBASE!Sleep()
  C:\build\ws\BUILDTYPE\Debug\LABEL\windows10\V\6-24\root\core\winnt\src\TWinNTSystem.cxx(4379): TWinNTSystem::TimerThread()
  C:\build\ws\BUILDTYPE\Debug\LABEL\windows10\V\6-24\root\core\winnt\inc\TWinNTSystem.h(99): TWinNTSystem::ThreadStub()
  KERNEL32!BaseThreadInitThunk()
  ntdll!RtlGetAppContainerNamedObjectPath()
  ntdll!RtlGetAppContainerNamedObjectPath()

================ Thread 2 ================
  win32u!NtUserGetMessage()
  C:\build\ws\BUILDTYPE\Debug\LABEL\windows10\V\6-24\root\core\winnt\src\TWinNTSystem.cxx(498): `anonymous namespace'::GUIThreadMessageProcessingLoop()
  KERNEL32!BaseThreadInitThunk()
  ntdll!RtlGetAppContainerNamedObjectPath()
  ntdll!RtlGetAppContainerNamedObjectPath()

================ Thread 3 ================
  ntdll!ZwWaitForWorkViaWorkerFactory()
  KERNEL32!BaseThreadInitThunk()
  ntdll!RtlGetAppContainerNamedObjectPath()
  ntdll!RtlGetAppContainerNamedObjectPath()

================ Thread 4 ================
  ntdll!ZwWaitForWorkViaWorkerFactory()
  KERNEL32!BaseThreadInitThunk()
  ntdll!RtlGetAppContainerNamedObjectPath()
  ntdll!RtlGetAppContainerNamedObjectPath()

==========================================
============= END STACKTRACE =============
==========================================

Any tips on this would be great
Thanks, Soren

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ROOT Version: 6.24
Platform: Windows 10
Compiler: Not Provided

2

You have to fit in order to get the function from the histogram. Try like this:

void fplot()
{
   TH1D* h1 = new TH1D("h1","",10,0,10);
   h1->SetBinContent(1, TMath::Poisson(0.,1));
   h1->SetBinContent(2, TMath::Poisson(0.,2));
   h1->SetBinContent(3, TMath::Poisson(0.,3));
   h1->SetBinContent(4, TMath::Poisson(0.,4));
   h1->SetBinContent(5, TMath::Poisson(0.,5));
   h1->SetBinContent(6, TMath::Poisson(0.,6));
   h1->SetBinContent(7, TMath::Poisson(0.,7));
   h1->SetBinContent(8, TMath::Poisson(0.,8));
   h1->SetBinContent(9, TMath::Poisson(0.,9));
   h1->SetBinContent(10,TMath::Poisson(0.,10));

   TF1 *Poisson = new TF1("Poisson", "TMath::Poisson([0],x)", 0., 10.);

   h1->Draw();
   h1->Fit("Poisson");

   TF1 *fit = h1->GetFunction("Poisson");
   if (fit) {
      double_t chi = fit->GetChisquare();
      cout << "ChiTest(1)" << chi << endl;
   } else {
      cout << "h1->GetFunction(\"Poisson\") failed" << endl;
   }
}