org.android.activityminer.model.configuration
Class MathUtils

java.lang.Object
  org.android.activityminer.model.configuration.MathUtils

public class MathUtils
extends Object

Class to hold mathematical constants & functions.

Field Summary

static Double	DOUBLE_NAN NaN Double constant
static Double	DOUBLE_NEGATIVE_INFINITY - infinity Double constant
static Double	DOUBLE_POSITIVE_INFINITY + infinity Double constant
static double	DOUBLE_PRECISION The double comparision precision
static Double	DOUBLE_ZERO Zero Double constant
static Integer	INTEGER_ZERO Zero Integer constant
static double	LOG2 The logarithm of two.
static Long	LONG_NEGATIVE_ONE -1 Long constant
static Long	LONG_ZERO Zero Long constant
static double	SQRT2 The square root of two.

Constructor Summary

MathUtils()

Method Summary

static double	conditionalRowEntropy(double[][] matrix) Computes the conditional not normalized(!)
static double	entropieFunction(double p) Entropy function wrapper to calculate p * log(p)
static double	entropy(double[] values) Does calculate the entropy for the given values.
static double	entropyFromEntropyValueSumAndTotalSum(double entropyValueSum, double totalValueSum) Method to calculate entropy from the sum of single entropy function values and the total value sum
static boolean	equalsWithPrecision(double x, double y) Does compare two double values with precision
static double	log2(double value) Calculates the logarithm for base 2
static double	mean(double[] values) Mean calculation.
static double	symmetricalUncertainty(double[][] matrix) Calculates the symmetrical uncertainty for a given matrix.
static double	variance(double[] values, double mean) Variance calculation.

Methods inherited from class java.lang.Object

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

Field Detail

LOG2

public static final double LOG2

The logarithm of two.

SQRT2

public static final double SQRT2

The square root of two.

DOUBLE_PRECISION

public static final double DOUBLE_PRECISION

The double comparision precision

See Also:

Constant Field Values

DOUBLE_ZERO

public static final Double DOUBLE_ZERO

Zero Double constant

DOUBLE_NAN

public static final Double DOUBLE_NAN

NaN Double constant

DOUBLE_POSITIVE_INFINITY

public static final Double DOUBLE_POSITIVE_INFINITY

+ infinity Double constant

DOUBLE_NEGATIVE_INFINITY

public static final Double DOUBLE_NEGATIVE_INFINITY

- infinity Double constant

INTEGER_ZERO

public static final Integer INTEGER_ZERO

Zero Integer constant

LONG_ZERO

public static final Long LONG_ZERO

Zero Long constant

LONG_NEGATIVE_ONE

public static final Long LONG_NEGATIVE_ONE

-1 Long constant

Constructor Detail

MathUtils

public MathUtils()

Method Detail

equalsWithPrecision

public static final boolean equalsWithPrecision(double x,
                                                double y)

Does compare two double values with precision

Parameters:

x - the first value

y - the second value

Returns:

true if difference is below double precision

entropy

public static final double entropy(double[] values)

Does calculate the entropy for the given values.

Parameters:

values - the values of the variable

Returns:

the entropy of the given values

entropyFromEntropyValueSumAndTotalSum

public static final double entropyFromEntropyValueSumAndTotalSum(double entropyValueSum,
                                                                 double totalValueSum)

Method to calculate entropy from the sum of single entropy function values and the total value sum

Parameters:

entropyValueSum - the sum of entropy function values

totalValueSum - the total value sum

Returns:

the entropy

entropieFunction

public static final double entropieFunction(double p)

Entropy function wrapper to calculate p * log(p)

Parameters:

p - the value

Returns:

p * log(p) if p > 0, 0 otherwise

log2

public static double log2(double value)

Calculates the logarithm for base 2

Parameters:

value -

Returns:

the logarithm for base 2

conditionalRowEntropy

public static final double conditionalRowEntropy(double[][] matrix)

Computes the conditional not normalized(!) entropy of the rows in the given matrix.

Parameters:

matrix - the matrix

Returns:

the conditional entropy

symmetricalUncertainty

public static final double symmetricalUncertainty(double[][] matrix)

Calculates the symmetrical uncertainty for a given matrix.

Parameters:

matrix - the matrix

Returns:

the symmetrical uncertainty

mean

public static double mean(double[] values)

Mean calculation.

Parameters:

values - the values

Returns:

the mean of the values

variance

public static double variance(double[] values,
                              double mean)

Variance calculation.

Parameters:

values - the values

mean - the mean of the values

Returns:

the variance of the values