Package org.apache.commons.math.stat.descriptive.summary

Class Product

java.lang.Object

org.apache.commons.math.stat.descriptive.AbstractUnivariateStatistic

org.apache.commons.math.stat.descriptive.AbstractStorelessUnivariateStatistic

org.apache.commons.math.stat.descriptive.summary.Product

All Implemented Interfaces:

java.io.Serializable, StorelessUnivariateStatistic, UnivariateStatistic, WeightedEvaluation

public class Product
extends AbstractStorelessUnivariateStatistic
implements java.io.Serializable, WeightedEvaluation

Returns the product of the available values.

If there are no values in the dataset, or any of the values are NaN, then NaN is returned.

Note that this implementation is not synchronized. If multiple threads access an instance of this class concurrently, and at least one of the threads invokes the increment() or clear() method, it must be synchronized externally.

Version:

$Revision: 1006299 $ $Date: 2010-10-10 16:47:17 +0200 (dim. 10 oct. 2010) $

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor	Description
Product()	Create a Product instance
Product(Product original)	Copy constructor, creates a new Product identical to the original

Method Summary

Modifier and Type	Method	Description
void	clear()	Clears the internal state of the Statistic
Product	copy()	Returns a copy of the statistic with the same internal state.
static void	copy(Product source, Product dest)	Copies source to dest.
double	evaluate(double[] values, double[] weights)	Returns the weighted product of the entries in the input array.
double	evaluate(double[] values, double[] weights, int begin, int length)	Returns the weighted product of the entries in the specified portion of the input array, or Double.NaN if the designated subarray is empty.
double	evaluate(double[] values, int begin, int length)	Returns the product of the entries in the specified portion of the input array, or Double.NaN if the designated subarray is empty.
long	getN()	Returns the number of values that have been added.
double	getResult()	Returns the current value of the Statistic.
void	increment(double d)	Updates the internal state of the statistic to reflect the addition of the new value.

Methods inherited from class org.apache.commons.math.stat.descriptive.AbstractStorelessUnivariateStatistic

equals, evaluate, hashCode, incrementAll, incrementAll

Methods inherited from class org.apache.commons.math.stat.descriptive.AbstractUnivariateStatistic

evaluate, getData, getDataRef, setData, setData, test, test

Methods inherited from class java.lang.Object

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

Constructor Detail

Product

public Product()

Create a Product instance

Product

public Product(Product original)

Copy constructor, creates a new Product identical to the original

Parameters:

original - the Product instance to copy

Method Detail

increment

public void increment(double d)

Updates the internal state of the statistic to reflect the addition of the new value.

Specified by:

increment in interface StorelessUnivariateStatistic

Specified by:

increment in class AbstractStorelessUnivariateStatistic

Parameters:

d - the new value.

getResult

public double getResult()

Returns the current value of the Statistic.

Specified by:

getResult in interface StorelessUnivariateStatistic

Specified by:

getResult in class AbstractStorelessUnivariateStatistic

Returns:

value of the statistic, Double.NaN if it has been cleared or just instantiated.

getN

public long getN()

Returns the number of values that have been added.

Specified by:

getN in interface StorelessUnivariateStatistic

Returns:

the number of values.

clear

public void clear()

Clears the internal state of the Statistic

Specified by:

clear in interface StorelessUnivariateStatistic

Specified by:

clear in class AbstractStorelessUnivariateStatistic

evaluate

public double evaluate(double[] values,
                       int begin,
                       int length)

Returns the product of the entries in the specified portion of the input array, or Double.NaN if the designated subarray is empty.

Throws IllegalArgumentException if the array is null.

Specified by:

evaluate in interface UnivariateStatistic

Overrides:

evaluate in class AbstractStorelessUnivariateStatistic

Parameters:

values - the input array

begin - index of the first array element to include

length - the number of elements to include

Returns:

the product of the values or Double.NaN if length = 0

Throws:

java.lang.IllegalArgumentException - if the array is null or the array index parameters are not valid

See Also:

UnivariateStatistic.evaluate(double[], int, int)

evaluate

public double evaluate(double[] values,
                       double[] weights,
                       int begin,
                       int length)

Returns the weighted product of the entries in the specified portion of the input array, or Double.NaN if the designated subarray is empty.

Throws IllegalArgumentException if any of the following are true:

• the values array is null
• the weights array is null
• the weights array does not have the same length as the values array
• the weights array contains one or more infinite values
• the weights array contains one or more NaN values
• the weights array contains negative values
• the start and length arguments do not determine a valid array

Uses the formula,

    weighted product = ∏values[i]weights[i]
 

that is, the weights are applied as exponents when computing the weighted product.

Specified by:

evaluate in interface WeightedEvaluation

Parameters:

values - the input array

weights - the weights array

begin - index of the first array element to include

length - the number of elements to include

Returns:

the product of the values or Double.NaN if length = 0

Throws:

java.lang.IllegalArgumentException - if the parameters are not valid

Since:

2.1

evaluate

public double evaluate(double[] values,
                       double[] weights)

Returns the weighted product of the entries in the input array.

Throws IllegalArgumentException if any of the following are true:

• the values array is null
• the weights array is null
• the weights array does not have the same length as the values array
• the weights array contains one or more infinite values
• the weights array contains one or more NaN values
• the weights array contains negative values

Uses the formula,

    weighted product = ∏values[i]weights[i]
 

that is, the weights are applied as exponents when computing the weighted product.

Specified by:

evaluate in interface WeightedEvaluation

Parameters:

values - the input array

weights - the weights array

Returns:

the product of the values or Double.NaN if length = 0

Throws:

java.lang.IllegalArgumentException - if the parameters are not valid

Since:

2.1

copy

public Product copy()

Returns a copy of the statistic with the same internal state.

Specified by:

copy in interface StorelessUnivariateStatistic

Specified by:

copy in interface UnivariateStatistic

Specified by:

copy in class AbstractStorelessUnivariateStatistic

Returns:

a copy of the statistic

copy

public static void copy(Product source,
                        Product dest)

Copies source to dest.

Neither source nor dest can be null.

Parameters:

source - Product to copy

dest - Product to copy to

Throws:

java.lang.NullPointerException - if either source or dest is null