class ROOT::Minuit2::FCNBase: public ROOT::Minuit2::GenericFunction




Interface (abstract class) defining the function to be minimized, which has to be implemented by the user.

@author Fred James and Matthias Winkler; modified by Andras Zsenei and Lorenzo Moneta

@ingroup Minuit


Function Members (Methods)

 
    This is an abstract class, constructors will not be documented.
    Look at the header to check for available constructors.

public:
virtual~FCNBase()
virtual doubleErrorDef() const
virtual doubleoperator()(const vector<double>& x) const
ROOT::Minuit2::FCNBase&operator=(const ROOT::Minuit2::FCNBase&)
virtual voidSetErrorDef(double)
virtual doubleUp() const

Class Charts

Inheritance Inherited Members Includes Libraries
Class Charts

Function documentation

virtual ~FCNBase()
{}
double operator()(const vector<double>& x) const

The meaning of the vector of parameters is of course defined by the user,
who uses the values of those parameters to calculate his function Value.
The order and the position of these parameters is strictly the one specified
by the user when supplying the starting values for minimization. The starting
values must be specified by the user, either via an std::vector<double> or the
MnUserParameters supplied as input to the MINUIT minimizers such as
VariableMetricMinimizer or MnMigrad. Later values are determined by MINUIT
as it searches for the Minimum or performs whatever analysis is requested by
the user.

@param par function parameters as defined by the user.

@return the Value of the function.

@see MnUserParameters
@see VariableMetricMinimizer
@see MnMigrad


double ErrorDef()

Error definition of the function. MINUIT defines Parameter errors as the
change in Parameter Value required to change the function Value by up. Normally,
for chisquared fits it is 1, and for negative log likelihood, its Value is 0.5.
If the user wants instead the 2-sigma errors for chisquared fits, it becomes 4,
as Chi2(x+n*sigma) = Chi2(x) + n*n.

Comment a little bit better with links!!!!!!!!!!!!!!!!!


{return Up();}
double Up()

Error definition of the function. MINUIT defines Parameter errors as the
change in Parameter Value required to change the function Value by up. Normally,
for chisquared fits it is 1, and for negative log likelihood, its Value is 0.5.
If the user wants instead the 2-sigma errors for chisquared fits, it becomes 4,
as Chi2(x+n*sigma) = Chi2(x) + n*n.

\todo Comment a little bit better with links!!!!!!!!!!!!!!!!! Idem for ErrorDef()


void SetErrorDef(double )
add interface to set dynamically a new error definition
Re-implement this funciton if needed.

{}

Last update: root/minuit2:$Id: FCNBase.h 21530 2007-12-20 11:14:35Z moneta $
Copyright (c) 2005 LCG ROOT Math team, CERN/PH-SFT *

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