Base class for random number distributions. More...

#include <Random.h>

Inheritance diagram for casa::Random:

Public Types
enum	Types { BINOMIAL, DISCRETEUNIFORM, ERLANG, GEOMETRIC, HYPERGEOMETRIC, NORMAL, LOGNORMAL, NEGATIVEEXPONENTIAL, POISSON, UNIFORM, WEIBULL, UNKNOWN, NUMBER_TYPES }
	This enumerator lists all the predefined random number distributions. More...
Public Member Functions
virtual	~Random ()
	A virtual destructor is needed to ensure that the destructor of derived classes gets used.
virtual Double	operator() ()=0
	This function returns a random number from the appropriate distribution.
RNG *	generator ()
	Functions that allow you to access and change the class that generates the random bits.
void	generator (RNG *p)
virtual void	setParameters (const Vector< Double > &parms)=0
	These function allow you to manipulate the parameters (mean variance etc.) of random number distribution.
virtual Vector< Double >	parameters () const =0
virtual Bool	checkParameters (const Vector< Double > &parms) const =0
Static Public Member Functions
static String	asString (Random::Types type)
	Convert the enumerator to a lower-case string.
static Random::Types	asType (const String &str)
	Convert the string to enumerator.
static Random *	construct (Random::Types type, RNG *gen)
	Convert the Random::Type enumerator to a specific object (derived from Random but upcast to a Random object).
static Vector< Double >	defaultParameters (Random::Types type)
	returns the default parameters for the specified distribution.
Protected Member Functions
	Random (RNG *generator)
Protected Attributes
RNG *	itsRNG

Detailed Description

Base class for random number distributions.

Intended use:

Public interface

Review Status

Reviewed By:: UNKNOWN
Date Reviewed:: before2004/08/25

Prerequisite

A knowledge of C++, in particular inheritance
College level mathematics

Synopsis

A random number generator may be declared by first constructing a RNG object and then a Random. For example,

      ACG gen(10, 20); 
      NegativeExpntl rnd (1.0, &gen);

declares an additive congruential generator with seed 10 and table size 20, that is used to generate exponentially distributed values with mean of 1.0.

The virtual member Random::operator() is the common way of extracting a random number from a particular distribution. The base class, Random does not implement operator(). This is performed by each of the derived classes. Thus, given the above declaration of rnd, new random values may be obtained via, for example, Double nextExpRand = rnd();

Currently, the following subclasses are provided:

Example

Thrown Exceptions

No exceptions are thrown directly from this class.

To Do

Nothing I hope!

Definition at line 425 of file Random.h.

Member Enumeration Documentation

enum casa::Random::Types

This enumerator lists all the predefined random number distributions.

Enumerator:

BINOMIAL	2 parameters. The binomial distribution models successfully drawing items from a pool. Specify n and p. n is the number of items in the pool, and p, is the probability of each item being successfully drawn. It is required that n > 0 and 0 <= p <= 1
DISCRETEUNIFORM	2 parameters. Model a uniform random variable over the closed interval. Specify the values low and high. The low parameter is the lowest possible return value and the high parameter is the highest. It is required that low < high.
ERLANG	2 parameters, mean and variance. It is required that the mean is non-zero and the variance is positive.
GEOMETRIC	1 parameters, the mean. It is required that 0 <= probability < 1
HYPERGEOMETRIC	2 parameters, mean and variance. It is required that the variance is positive and that the mean is non-zero and not bigger than the square-root of the variance.
NORMAL	2 parameters, the mean and variance. It is required that the variance is positive.
LOGNORMAL	2 parameters, mean and variance. It is required that the supplied variance is positive and that the mean is non-zero
NEGATIVEEXPONENTIAL	1 parameter, the mean.
POISSON	1 parameter, the mean. It is required that the mean is non-negative
UNIFORM	2 parameters, low and high. Model a uniform random variable over the closed interval. The low parameter is the lowest possible return value and the high parameter can never be returned. It is required that low < high.
WEIBULL	2 parameters, alpha and beta. It is required that the alpha parameter is not zero.
UNKNOWN	An non-predefined random number distribution.
NUMBER_TYPES	Number of distributions.

Definition at line 429 of file Random.h.

Constructor & Destructor Documentation

virtual casa::Random::~Random ( ) [virtual]

A virtual destructor is needed to ensure that the destructor of derived classes gets used.

Not that this destructor does NOT delete the pointer to the RNG object

casa::Random::Random ( RNG * generator ) [inline, protected]

Definition at line 538 of file Random.h.

References itsRNG.

Member Function Documentation

static String casa::Random::asString ( Random::Types type ) [static]

Convert the enumerator to a lower-case string.

static Random::Types casa::Random::asType ( const String & str ) [static]

Convert the string to enumerator.

The parsing of the string is case insensitive. Returns the Random::UNKNOWN value if the string does not cotrtrespond to any of the enumerators.

virtual Bool casa::Random::checkParameters ( const Vector< Double > & parms ) const [pure virtual]

Implemented in casa::Weibull, casa::Uniform, casa::Poisson, casa::NegativeExpntl, casa::LogNormal, casa::Normal, casa::HyperGeometric, casa::Geometric, casa::Erlang, casa::DiscreteUniform, and casa::Binomial.

static Random* casa::Random::construct	(	Random::Types	type,
		RNG *	gen
	)		`[static]`

Convert the Random::Type enumerator to a specific object (derived from Random but upcast to a Random object).

Returns a null pointer if the object could not be constructed. This will occur is the enumerator is UNKNOWN or NUMBER_TYPES or there is insufficient memory. The caller of this function is responsible for deleting the pointer.

static Vector<Double> casa::Random::defaultParameters ( Random::Types type ) [static]

returns the default parameters for the specified distribution.

Returns an empty Vector if a non-predifined distribution is used.

RNG * casa::Random::generator ( ) [inline]

Functions that allow you to access and change the class that generates the random bits.

Definition at line 543 of file Random.h.

References itsRNG.

void casa::Random::generator ( RNG * p ) [inline]

Definition at line 548 of file Random.h.

References itsRNG.

virtual Double casa::Random::operator() ( ) [pure virtual]

This function returns a random number from the appropriate distribution.

Implemented in casa::Weibull, casa::Uniform, casa::Poisson, casa::NegativeExpntl, casa::LogNormal, casa::Normal, casa::HyperGeometric, casa::Geometric, casa::Erlang, casa::DiscreteUniform, and casa::Binomial.

virtual Vector<Double> casa::Random::parameters ( ) const [pure virtual]

Implemented in casa::Weibull, casa::Uniform, casa::Poisson, casa::NegativeExpntl, casa::LogNormal, casa::Normal, casa::HyperGeometric, casa::Geometric, casa::Erlang, casa::DiscreteUniform, and casa::Binomial.

virtual void casa::Random::setParameters ( const Vector< Double > & parms ) [pure virtual]

These function allow you to manipulate the parameters (mean variance etc.) of random number distribution.

The parameters() function returns the current value, the setParameters function allows you to change the parameters and the checkParameters function will return False if the supplied parameters are not appropriate for the distribution.

Implemented in casa::Weibull, casa::Uniform, casa::Poisson, casa::NegativeExpntl, casa::LogNormal, casa::Normal, casa::HyperGeometric, casa::Geometric, casa::Erlang, casa::DiscreteUniform, and casa::Binomial.

Member Data Documentation

RNG* casa::Random::itsRNG [protected]

Definition at line 535 of file Random.h.

Referenced by generator(), and Random().

The documentation for this class was generated from the following file:

casacore/casa/BasicMath/Random.h

Public Types

Public Member Functions

Static Public Member Functions

Protected Member Functions

Protected Attributes

Detailed Description

Intended use:

Review Status

Prerequisite

Synopsis

Example

Thrown Exceptions

To Do

Member Enumeration Documentation

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation