class TUnuranDiscrDist: public TUnuranBaseDist


TUnuranDiscrDist class for one dimensional discrete distribution.
It is used by TUnuran to generate integer random numbers according to this distribution via
TUnuran::SampleDiscr().

The class can be constructed from a one-dimensional function (TF1 pointer)
representing the discrete distribution (probability mesh function)
(for example a TF1("f","TMath::PoissonI(x,[0])") ) or from a
vector of probability, used by passing an iterator specifying the begin and the end of the vector.
In the latter case the domain of the distribution will be defined by the vector, while in the first case is by
default (0,+inf).
a Method to set the domain of the distribution ( SetDomain ) is provided and it defines the range
of the generated random numbers.

The derivatives of the pdf which are used by some UNURAN methods are estimated numerically in the
Derivative() method.
Some extra information (like distribution mode, cdf function, probability sum, etc..)
can be set as well otherwise will be estimated internally if required.

Function Members (Methods)

public:

	TUnuranDiscrDist(TF1* func = 0)
	TUnuranDiscrDist(const TUnuranDiscrDist&)
	TUnuranDiscrDist(double* begin, double* end)
virtual	~TUnuranDiscrDist()
double	Cdf(int x) const
static TClass*	Class()
virtual TUnuranDiscrDist*	Clone() const
bool	GetDomain(int& xmin, int& xmax) const
bool	HasCdf() const
bool	HasMode() const
bool	HasProbSum() const
virtual TClass*	IsA() const
int	Mode() const
TUnuranDiscrDist&	operator=(const TUnuranDiscrDist& rhs)
double	Pmf(int x) const
double	ProbSum() const
const vector<double>&	ProbVec() const
void	SetCdf(TF1* cdf)
void	SetDomain(int xmin, int xmax)
void	SetMode(int mode)
void	SetProbSum(double sum)
virtual void	ShowMembers(TMemberInspector& insp, char* parent)
virtual void	Streamer(TBuffer& b)
void	StreamerNVirtual(TBuffer& b)

Data Members

private:

TF1*	fCdf	pointer to the cumulative distribution function
bool	fHasDomain	flag to control if distribution has a defined domain (otherwise is [0,INT_MAX])
bool	fHasMode	flag to control if distribution has a pre-computed mode
bool	fHasSum	flag to control if distribution has a pre-computed sum of the probabilities
int	fMode	mode of the distribution
vector<double>	fPVec	Vector of the probabilities
TF1*	fPmf	pointer to a function calculating the probability
double	fSum	total sum of the probabilities in the given domain
double	fX[1]	! cached vector for using TF1::EvalPar
int	fXmax	upper value of the domain
int	fXmin	lower value of the domain

Class Charts

Function documentation

TUnuranDiscrDist(double* begin, double* end)

Constructor from a vector of probability

{}

~TUnuranDiscrDist()

Destructor (no operations)

{}

TUnuranDiscrDist * Clone()

Clone (required by base class)

{ return new TUnuranDiscrDist(*this); }

void SetCdf(TF1* cdf)

set cdf distribution. If a method requires it
and is not set it is estimated numerically

{ fCdf = cdf; }

void SetDomain(int xmin, int xmax)

Set the distribution domain, by default the domain is [0,INT_MAX]
If xmin >= xmax a domain is removed

void SetMode(int mode)

set the mode of the distribution (location of maximum probability)

{ fMode = mode; fHasMode=true;}

void SetProbSum(double sum)

set the value of the sum of the probabilities in the given domain

{ fSum = sum; fHasSum=true; }

int Mode()

get the mode   (x location of function maximum)

{ return fMode; }

double ProbSum()

return area of the pdf

{ return fSum; }

bool HasMode()

flag to control if distribution provides the mode

{ return fHasMode; }

bool HasProbSum()

flag to control if distribution provides the total area of the probability function

{ return fHasSum; }

bool HasCdf()

flag to control if distribution provides also a Cdf

{ return fCdf != 0; }

const std::vector<double> & ProbVec()

retrieve a reference to the vector of the probabilities : Prob(i)
If the distribution is defined from a function (i.e. for distribution with undefined domain)
the vector is empty.

{ return fPVec; }

double Pmf(int x) const

evaluate the distribution (probability mesh function) at the integer value x.
Used internally by UnuRan
For integer values outside the domain the function must return 0.0