ChemotaxisUtil::GammaSampler Class Reference

#include <util.hh>

List of all members.

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Detailed Description

Generates random numbers sampled from a gamma distribution.

A nice implementation of an algorithm that samples from a gamma distributionwith code modified from the book :

Press, Teukolsky, Vetterling, and Flannery. "Numerical Recipes, The art of Scientific Computing", Third Edition. 2007 Cambridge University Press.

It additionally has a parameter that allows the entire distribution to be shifted by a given amount and a generate function that resamples until the chosen number is within a particular range. In the chemotaxis model, this code is used primarily to choose a new random angle from the distribution of changes in direction (fig 3 from Berg & Brown, Chemotaxis in Escherichia coli analysed by Three-dimensional Tracking, Nature, volume 239, (1972) )

Public Member Functions
	GammaSampler (double alpha, double beta)
	GammaSampler (double alpha, double beta, double meanShift)
double	gen ()
double	gen (double minAcceptableValue, double maxAcceptableValue)
Protected Attributes
double	alpha
double	oalpha
double	beta
double	a1
double	a2
double	meanShift

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Constructor & Destructor Documentation

GammaSampler::GammaSampler	(	double	alpha,
		double	beta
	)

Constructor to generate a basic gamma distribution.

Parameters:

	alpha	the alpha parameter (note, alpha=k=shape).
	beta	the beta parameter (note, beta=1/theta=1/scale).

GammaSampler::GammaSampler	(	double	alpha,
		double	beta,
		double	meanShift
	)

Constructor to generate a gamma distribution that is shifted by the given amount.

Parameters:

	alpha	the alpha parameter (note, alpha=k=shape).
	beta	the beta parameter (note, beta=1/theta=1/scale).
	meanShift	shifts the entire distribution by this amount.

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Member Function Documentation

double GammaSampler::gen

(

)

Generates a new random number (using the NFutil Mersenne Twister random number generator) sampled from the initialized gamma distribution.

double GammaSampler::gen	(	double	minAcceptableValue,
		double	maxAcceptableValue
	)

Generates a new random number (using the NFutil Mersenne Twister random number generator) sampled from the initialized gamma distribution that lies within (inclusive) of the range given. Carefull here! Your range should be such that it doesn't take forever to find a number in the range!

Parameters:

	minAcceptableValue	the minimum random value this function will return.
	maxAcceptableValue	the maximum random value this function will return.

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Member Data Documentation

double ChemotaxisUtil::GammaSampler::alpha [protected]

double ChemotaxisUtil::GammaSampler::oalpha [protected]

double ChemotaxisUtil::GammaSampler::beta [protected]

double ChemotaxisUtil::GammaSampler::a1 [protected]

double ChemotaxisUtil::GammaSampler::a2 [protected]

double ChemotaxisUtil::GammaSampler::meanShift [protected]

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

• /home/msneddon/eclipse/galileoSR1_cpp/workspace/NFsim/src/NFtest/agentcell/cell/util.hh
• /home/msneddon/eclipse/galileoSR1_cpp/workspace/NFsim/src/NFtest/agentcell/cell/util.cpp

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