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Reference Guide
MnParameterScan.cxx
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1 // @(#)root/minuit2:$Id$
2 // Authors: M. Winkler, F. James, L. Moneta, A. Zsenei 2003-2005
3 
4 /**********************************************************************
5  * *
6  * Copyright (c) 2005 LCG ROOT Math team, CERN/PH-SFT *
7  * *
8  **********************************************************************/
9 
11 #include "Minuit2/FCNBase.h"
12 
13 namespace ROOT {
14 
15  namespace Minuit2 {
16 
17 
18 MnParameterScan::MnParameterScan(const FCNBase& fcn, const MnUserParameters& par) : fFCN(fcn), fParameters(par), fAmin(fcn(par.Params())) {}
19 
20 MnParameterScan::MnParameterScan(const FCNBase& fcn, const MnUserParameters& par, double fval) : fFCN(fcn), fParameters(par), fAmin(fval) {}
21 
22 std::vector<std::pair<double, double> > MnParameterScan::operator()(unsigned int par, unsigned int maxsteps, double low, double high) {
23  // do the scan for parameter par between low and high values
24 
25  //if(maxsteps > 101) maxsteps = 101;
26  std::vector<std::pair<double, double> > result; result.reserve(maxsteps+1);
27  std::vector<double> params = fParameters.Params();
28  result.push_back(std::pair<double, double>(params[par], fAmin));
29 
30  if(low > high) return result;
31  if(maxsteps < 2) return result;
32 
33  if(low == 0. && high == 0.) {
34  low = params[par] - 2.*fParameters.Error(par);
35  high = params[par] + 2.*fParameters.Error(par);
36  }
37 
38  if(low == 0. && high == 0. && fParameters.Parameter(par).HasLimits()) {
40  low = fParameters.Parameter(par).LowerLimit();
42  high = fParameters.Parameter(par).UpperLimit();
43  }
44 
45  if(fParameters.Parameter(par).HasLimits()) {
47  low = std::max(low, fParameters.Parameter(par).LowerLimit());
49  high = std::min(high, fParameters.Parameter(par).UpperLimit());
50  }
51 
52  double x0 = low;
53  double stp = (high - low)/double(maxsteps - 1);
54  for(unsigned int i = 0; i < maxsteps; i++) {
55  params[par] = x0 + double(i)*stp;
56  double fval = fFCN(params);
57  if(fval < fAmin) {
58  fParameters.SetValue(par, params[par]);
59  fAmin = fval;
60  }
61  result.push_back(std::pair<double, double>(params[par], fval));
62  }
63 
64  return result;
65 }
66 
67  } // namespace Minuit2
68 
69 } // namespace ROOT
Namespace for new ROOT classes and functions.
Definition: StringConv.hxx:21
std::vector< std::pair< double, double > > operator()(unsigned int par, unsigned int maxsteps=41, double low=0., double high=0.)
void SetValue(unsigned int, double)
Interface (abstract class) defining the function to be minimized, which has to be implemented by the ...
Definition: FCNBase.h:47
API class for the user interaction with the parameters; serves as input to the minimizer as well as o...
double Error(unsigned int) const
const MinuitParameter & Parameter(unsigned int) const
access to single Parameter
MnParameterScan(const FCNBase &, const MnUserParameters &)
std::vector< double > Params() const
access to parameters and errors in column-wise representation