bham.leakiest.infotheory

Class InfoTheory

java.lang.Object

bham.leakiest.infotheory.InfoTheory

public class InfoTheory
extends java.lang.Object

This is a library of useful information theory definitions. Most are complete standard, see for example "Elements of Information Theory" by Cover and Thomas.
Probability Mass Functions are represented by an array of doubles p(element i) = pmf[i] or by ProbDist class.

Version:

1.4.5

Author:

Tom Chothia, Yusuke Kawamoto

Field Summary

Fields

Modifier and Type	Field and Description
static int	base_log Base when computing the logarithms.

Constructor Summary

Constructors

Constructor and Description
InfoTheory()

Method Summary

Modifier and Type	Method and Description
static double	log(double x, int base) Calculates the logarithm of input x w.r.t any base.
static double	log2(double x) Calculates the logarithm of input x w.r.t base 2.
static double	log2Multi(double x, double y) Calculates the logarithm of input x w.r.t base 2, multiplied by y, where 0 log 0 = 0.
static double	logMulti(double x, int base, double y) Calculates the logarithm of input x w.r.t any base, multiplied by y, where 0 log 0 = 0.
static double	mean(double[] Data) This method returns the mean of given data.
static double	median(double[] Data) This method returns the median of given data.
static double[]	outputDist(double[] inputDist, double[][] matrix) Calculate the marginal output probability distribution P_Y from a given input distribution inputDist and a given channel matrix matrix.
static double	outputProb(int outputIndex, double[] Q, double[][] W) Finds the change of output elementIndex using P_Y(y) = R(y) = QW(y) = Σ_x W(y|x)Q(x).
static void	printPMF(double[] probs) Prints the probability distribution probs with where element a_i has prob[i], to 4 decimal places.
static void	printPMF(java.lang.String[] names, double[] probs) Prints the probability distribution probs with where element names[i] has prob[i].
static double[]	uniformDist(int noOfElements) Calculates the uniform distribution of length "noOfElements".

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

base_log

public static final int base_log

Base when computing the logarithms.

See Also:

Constant Field Values

Constructor Detail

InfoTheory

public InfoTheory()

Method Detail

log

public static double log(double x,
                         int base)

Calculates the logarithm of input x w.r.t any base.

Parameters:

x - the real number whose logarithm is calculated.

base - The base w.r.t. which logarithm is calculated.

Returns:

the logarithm of input x w.r.t base.

log2

public static double log2(double x)

Calculates the logarithm of input x w.r.t base 2.

Parameters:

x - the real number whose logarithm is calculated.

Returns:

the logarithm of input x w.r.t base 2.

log2Multi

public static double log2Multi(double x,
                               double y)

Calculates the logarithm of input x w.r.t base 2, multiplied by y, where 0 log 0 = 0.

Parameters:

x - the real number whose logarithm is calculated.

y - the real number that multiplies log_2 x

Returns:

the logarithm of input x w.r.t base 2.

logMulti

public static double logMulti(double x,
                              int base,
                              double y)

Calculates the logarithm of input x w.r.t any base, multiplied by y, where 0 log 0 = 0.

Parameters:

x - the real number whose logarithm is calculated.

base - the base w.r.t. which logarithm is calculated.

y - the real number that multiplies log_{base} x

Returns:

the logarithm of input x w.r.t base.

mean

public static double mean(double[] Data)

This method returns the mean of given data.

Parameters:

Data - data array

Returns:

the mean of the data

median

public static double median(double[] Data)

This method returns the median of given data.

Parameters:

Data - data array

Returns:

the median of the data

outputDist

public static double[] outputDist(double[] inputDist,
                                  double[][] matrix)

Calculate the marginal output probability distribution P_Y from a given input distribution inputDist and a given channel matrix matrix.

Parameters:

inputDist - input distribution array

matrix - channel matrix array

Returns:

the marginal output probability distribution

outputProb

public static double outputProb(int outputIndex,
                                double[] Q,
                                double[][] W)

Finds the change of output elementIndex using P_Y(y) = R(y) = QW(y) = Σ_x W(y|x)Q(x).

Parameters:

outputIndex - output index of the channel matrix W

Q - input PMF array

W - channel matrix

Returns:

the sum of joint probability for outputIndex

printPMF

public static void printPMF(double[] probs)

Prints the probability distribution probs with where element a_i has prob[i], to 4 decimal places.

Parameters:

probs - array of PMF

printPMF

public static void printPMF(java.lang.String[] names,
                            double[] probs)

Prints the probability distribution probs with where element names[i] has prob[i].

Parameters:

names - array of labels

probs - array of PMF

uniformDist

public static double[] uniformDist(int noOfElements)

Calculates the uniform distribution of length "noOfElements".

Parameters:

noOfElements - the number of elements in the uniform distribution.

Returns:

the uniform distribution of length "noOfElements".