ROOT   Reference Guide
FumiliChi2FCN.h
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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
10#ifndef ROOT_Minuit2_FumiliChi2FCN
11#define ROOT_Minuit2_FumiliChi2FCN
12
13#include "FumiliFCNBase.h"
14#include <vector>
16
17namespace ROOT {
18
19 namespace Minuit2 {
20
21
22
23/**
24
25Extension of the FCNBase for the Fumili method. Fumili applies only to
26minimization problems used for fitting. The method is based on a
27linearization of the model function negleting second derivatives.
28User needs to provide the model function. The figure-of-merit describing
29the difference between the model function and the actual measurements in
30the case of chi-square is the sum of the squares of the figures-of-merit
31calculated for each measurement point, which is implemented by the
32operator() member function. The user still has to implement the calculation
33of the individual figures-of-merit (which in the majority of the cases
34will be the (measured Value - the Value predicted by the model)/standard deviation
35implemeted by the FumiliStandardChi2FCN;
36however this form can become more complicated (see for an example Numerical Recipes'
37section on "Straight-Line Data with Errors in Both Coordinates")).
38
39
40@author Andras Zsenei and Lorenzo Moneta, Creation date: 24 Aug 2004
41
42@see <A HREF="http://www.cern.ch/winkler/minuit/tutorial/mntutorial.pdf">MINUIT Tutorial</A> on function minimization, section 5
43
44@see FumiliStandardChi2FCN
45
46@ingroup Minuit
47
48*/
49
50
51
53
54public:
55
57
58 virtual ~FumiliChi2FCN() {}
59
60
61 /**
62
63 Sets the model function for the data (for example gaussian+linear for a peak)
64
65 @param modelFunction a reference to the model function.
66
67 */
68
69 void SetModelFunction(const ParametricFunction& modelFCN) { fModelFunction = &modelFCN; }
70
71
72
73 /**
74
75 Returns the model function used for the data.
76
77 @return Returns a pointer to the model function.
78
79 */
80
82
83
84
85 /**
86
87 Evaluates the model function for the different measurement points and
88 the Parameter values supplied, calculates a figure-of-merit for each
89 measurement and returns a vector containing the result of this
90 evaluation.
91
92 @param par vector of Parameter values to feed to the model function.
93
94 @return A vector containing the figures-of-merit for the model function evaluated
95 for each set of measurements.
96
97 */
98
99 virtual std::vector<double> Elements(const std::vector<double>& par) const = 0;
100
101
102
103 /**
104
105 Accessor to the parameters of a given measurement. For example in the
106 case of a chi-square fit with a one-dimensional Gaussian, the Parameter
107 characterizing the measurement will be the position. It is the Parameter
108 that is feeded to the model function.
109
110 @param Index Index of the measueremnt the parameters of which to return
111 @return A reference to a vector containing the values characterizing a measurement
112
113 */
114
115 virtual const std::vector<double> & GetMeasurement(int Index) const = 0;
116
117
118 /**
119
120 Accessor to the number of measurements used for calculating the
121 present figure of merit.
122
123 @return the number of measurements
124
125 */
126
127 virtual int GetNumberOfMeasurements() const = 0;
128
129
130
131 /**
132
133 Calculates the sum of Elements squared, ie the chi-square. The user must
134 implement in a class which inherits from FumiliChi2FCN the member function
135 Elements() which will supply the Elements for the sum.
136
137
138 @param par vector containing the Parameter values for the model function
139
140 @return The sum of Elements squared
141
142 @see FumiliFCNBase#elements
143
144 */
145
146 double operator()(const std::vector<double>& par) const {
147
148 double chiSquare = 0.0;
149 std::vector<double> vecElements = Elements(par);
150 unsigned int vecElementsSize = vecElements.size();
151
152 for (unsigned int i = 0; i < vecElementsSize; ++i)
153 chiSquare += vecElements[i]*vecElements[i];
154
155 return chiSquare;
156 }
157
158
159
160 /**
161
162 !!!!!!!!!!!! to be commented
163
164 */
165
166 virtual double Up() const { return 1.0; }
167
168 private:
169
170 // A pointer to the model function which describes the data
172
173
174
175};
176
177 } // namespace Minuit2
178
179} // namespace ROOT
180
181#endif // ROOT_Minuit2_FumiliChi2FCN
Extension of the FCNBase for the Fumili method.
Definition: FumiliChi2FCN.h:52
void SetModelFunction(const ParametricFunction &modelFCN)
Sets the model function for the data (for example gaussian+linear for a peak)
Definition: FumiliChi2FCN.h:69
const ParametricFunction * fModelFunction
const ParametricFunction * ModelFunction() const
Returns the model function used for the data.
Definition: FumiliChi2FCN.h:81
virtual double Up() const
!!!!!!!!!!!! to be commented
virtual std::vector< double > Elements(const std::vector< double > &par) const =0
Evaluates the model function for the different measurement points and the Parameter values supplied,...
double operator()(const std::vector< double > &par) const
Calculates the sum of Elements squared, ie the chi-square.
virtual const std::vector< double > & GetMeasurement(int Index) const =0
Accessor to the parameters of a given measurement.
virtual int GetNumberOfMeasurements() const =0
Accessor to the number of measurements used for calculating the present figure of merit.
Extension of the FCNBase for the Fumili method.
Definition: FumiliFCNBase.h:47
Function which has parameters.
VSD Structures.
Definition: StringConv.hxx:21
RooCmdArg Index(RooCategory &icat)