/*****************************************************************************
 * Project: RooFit                                                           *
 * Package: RooFitCore                                                       *
 * @(#)root/roofitcore:$Id: RooPullVar.cxx 24285 2008-06-16 15:05:15Z wouter $
 * Authors:                                                                  *
 *   WV, Wouter Verkerke, UC Santa Barbara, verkerke@slac.stanford.edu       *
 *   DK, David Kirkby,    UC Irvine,         dkirkby@uci.edu                 *
 *                                                                           *
 * Copyright (c) 2000-2005, Regents of the University of California          *
 *                          and Stanford University. All rights reserved.    *
 *                                                                           *
 * Redistribution and use in source and binary forms,                        *
 * with or without modification, are permitted according to the terms        *
 * listed in LICENSE (http://roofit.sourceforge.net/license.txt)             *
 *****************************************************************************/

//////////////////////////////////////////////////////////////////////////////
//
// BEGIN_HTML
// Class RooPullVar represents the pull of measurement w.r.t to true value
// using the measurement value and its error. Both the true value and
// the measured value (with error) are taken from two user supplied
// RooRealVars. If an asymmetric error is defined on a given measurement the proper 
// side of that asymmetric error will be used
// END_HTML
//

#include "RooFit.h"

#include "Riostream.h"
#include "Riostream.h"
#include <math.h>

#include "RooPullVar.h"
#include "RooAbsReal.h"
#include "RooRealVar.h"

ClassImp(RooPullVar)
;


//_____________________________________________________________________________
RooPullVar::RooPullVar()
{
  // Default constructor
}



//_____________________________________________________________________________
RooPullVar::RooPullVar(const char* name, const char* title, RooRealVar& meas, RooAbsReal& truth) :
  RooAbsReal(name, title),
  _meas("meas","Measurement",this,meas),
  _true("true","Truth",this,truth)
{
  // Construct RooAbsReal representing the pull of a RooRealVar 'meas' providing the
  // measured value and its error and a RooAbsReal 'truth' providing the true value
}





//_____________________________________________________________________________
RooPullVar::RooPullVar(const RooPullVar& other, const char* name) :
  RooAbsReal(other, name), 
  _meas("meas",this,other._meas),
  _true("true",this,other._true)
{
  // Copy constructor
}



//_____________________________________________________________________________
RooPullVar::~RooPullVar() 
{
  // Destructor
}



//_____________________________________________________________________________
Double_t RooPullVar::evaluate() const 
{
  // Calculate pull. Use asymmetric error if defined in measurement,
  // otherwise use symmetric error. If measurement has no error
  // return zero.

  const RooRealVar& meas = static_cast<const RooRealVar&>(_meas.arg()) ;  
  if (meas.hasAsymError()) {
    Double_t delta = _meas-_true ;
    if (delta<0) {
      return delta/meas.getAsymErrorHi() ;
    } else {
      return -delta/meas.getAsymErrorLo() ;
    }
  } else if (meas.hasError()) {
    return (_meas-_true)/meas.getError() ;    
  } else {
    return 0 ;
  }
}