Look at the header to check for available constructors.

virtual | ~FCNBase() |

virtual double | ErrorDef() const |

virtual double | operator()(const vector<double>& x) const |

ROOT::Minuit2::FCNBase& | operator=(const ROOT::Minuit2::FCNBase&) |

virtual void | SetErrorDef(double) |

virtual double | Up() const |

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.

`{}`