org.openimaj.math.util

Class DoubleArrayStatsUtils

java.lang.Object

org.openimaj.math.util.DoubleArrayStatsUtils

public class DoubleArrayStatsUtils
extends Object

Some basic statistical operations on double arrays

Author:

Sina Samangooei (ss@ecs.soton.ac.uk)

Constructor Summary

Constructors

Constructor and Description
DoubleArrayStatsUtils()

Method Summary

Modifier and Type	Method and Description
static double	mean(double[] arr) Find the mean of a single dimensional double array.
static double	mean(double[][] arr) Calculate the mean of a two dimensional double array.
static double	median(double[] arr) Calculate the median of the given array.
static double	median(double[] arr, int start, int stop) Calculate the median of the given sub-array.
static double	std(double[] arr) Calculate the sample standard deviation of a 1D array.
static double	std(double[][] arr) Calculate the sample standard deviation of a 2D array.
static double	sum(double[] arr) Calculate the sum of a 1D array.
static double	sum(double[][] arr) Calculate the sum of a 2D array.
static double	sumAbs(double[] arr) Calculate the sum the absolute values of a 1D array.
static double	sumAbs(double[][] arr) Calculate the sum of the absolute values of a 2D array.
static double	sumSq(double[] arr) Calculate the sum the squared values of a 1D array.
static double	sumSq(double[][] arr) Calculate the sum of the squared values of a 2D array.
static double	var(double[] arr) Calculate the sample variance of a one dimensional double array.
static double	var(double[][] arr) Calculate the sample variance of a one dimensional double array.

Methods inherited from class java.lang.Object

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

Constructor Detail

DoubleArrayStatsUtils

public DoubleArrayStatsUtils()

Method Detail

mean

public static double mean(double[] arr)

Find the mean of a single dimensional double array. returns 0 if the array is empty.

Parameters:

arr -

Returns:

the mean

mean

public static double mean(double[][] arr)

Calculate the mean of a two dimensional double array. returns 0 if the array is empty.

Parameters:

arr -

Returns:

the mean

var

public static double var(double[] arr)

Calculate the sample variance of a one dimensional double array. If the length of the array is less than 2, variance is 0.

Parameters:

arr -

Returns:

the variance

var

public static double var(double[][] arr)

Calculate the sample variance of a one dimensional double array. If the length of the array is less than 2, variance is 0.

Parameters:

arr -

Returns:

the variance

std

public static double std(double[][] arr)

Calculate the sample standard deviation of a 2D array. Calls var(double[][]) and does a Math.sqrt.

Parameters:

arr -

Returns:

the standard deviation

std

public static double std(double[] arr)

Calculate the sample standard deviation of a 1D array. Calls var(double[]) and does a Math.sqrt.

Parameters:

arr -

Returns:

the standard deviation

sum

public static double sum(double[][] arr)

Calculate the sum of a 2D array.

Parameters:

arr -

Returns:

the sum

sum

public static double sum(double[] arr)

Calculate the sum of a 1D array.

Parameters:

arr -

Returns:

the sum

sumSq

public static double sumSq(double[][] arr)

Calculate the sum of the squared values of a 2D array.

Parameters:

arr -

Returns:

sum of squares

sumSq

public static double sumSq(double[] arr)

Calculate the sum the squared values of a 1D array.

Parameters:

arr -

Returns:

sum of squares

sumAbs

public static double sumAbs(double[][] arr)

Calculate the sum of the absolute values of a 2D array.

Parameters:

arr -

Returns:

the sum absolute values

sumAbs

public static double sumAbs(double[] arr)

Calculate the sum the absolute values of a 1D array.

Parameters:

arr -

Returns:

the sum absolute values

median

public static double median(double[] arr)

Calculate the median of the given array. Uses the quick select algorithm (ArrayUtils.quickSelect(double[], int)).

Parameters:

arr - the array

Returns:

the median value

median

public static double median(double[] arr,
                            int start,
                            int stop)

Calculate the median of the given sub-array. Uses the quick select algorithm (ArrayUtils.quickSelect(double[], int, int, int)).

Parameters:

arr - the array

start - starting point in the array (inclusive)

stop - stopping point in the array (exclusive)

Returns:

the median value