org.josef.science.math

Class CStatistics

java.lang.Object

org.josef.science.math.CStatistics

@Status(stage=PRODUCTION,
        unitTests=COMPLETE)
 @Review(by="Kees Schotanus",
        at="2009-09-28")
 @Wish(value="Add Kurtosis") @Wish(value="Add linear regression")
 @ThreadSafety(level=IMMUTABLE)
public final class CStatistics
extends Object

Mathematical utility class to calculate statistical values like average and minimum value and maximum value of a list of values.

Version:

1.0 $Revision: 6488 $

Author:

Kees Schotanus

Method Summary

Modifier and Type	Method and Description
static CStatistics	computeStatistics(boolean sample, double... data) Computes the mathematical statistics for the supplied values.
double	getAverage() Gets the average value of the data.
double[]	getData() Gets (a copy of) the statistical data.
double	getMaximum() Gets the maximum value from the data.
double	getMedian() Gets the median value of the data.
double	getMinimum() Gets the minimum value from the data.
double	getSkewness() Computes the skewness (symmetry) of the data.
double	getStandardDeviation() Gets the standard deviation of the data.
double	getSum() Gets the sum of all the values in the data.
double	getVariance() Gets the variance of the data.

Methods inherited from class java.lang.Object

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

Method Detail

computeStatistics

public static CStatistics computeStatistics(boolean sample,
                                            double... data)

Computes the mathematical statistics for the supplied values.

Parameters:

sample - Determines whether the data is a sample or a complete population.

data - The input values to compute the statistics for.

Returns:

The statistical data.

Throws:

NullPointerException - When the supplied values is null.

IllegalArgumentException - When the supplied values is empty.

getData

public double[] getData()

Gets (a copy of) the statistical data.

Returns:

A copy of the statistical data.

getMinimum

public double getMinimum()

Gets the minimum value from the data.

Returns:

The minimum value from the data.

getMaximum

public double getMaximum()

Gets the maximum value from the data.

Returns:

The maximum value from the data.

getSum

public double getSum()

Gets the sum of all the values in the data.

Returns:

The sum of all the values in the data.

getAverage

public double getAverage()

Gets the average value of the data.

Returns:

The average value of the data.

getMedian

public double getMedian()

Gets the median value of the data.
When the number of values in the data is odd the median value is simply the value at the middle of the data, provided that the data is sorted. When the number of values is even the median is defined as the average value of both values that are in the middle of the data, again provided the data is sorted.
Example 1: The median of: 1,3,4,1 can be computed as follows. Sort the list, the result is: 1,1,3,4. Since the number of values in the list is even we have to compute the average of the two numbers in the middle (1 and 3) resulting in the answer: 2.
Example 2: The median of: 1,3,5,7,9 is 5. The number of values is odd so the median is simply the middle value which is 5.

Returns:

The median value of the data.

getVariance

public double getVariance()

Gets the variance of the data.
The variance is defined as the average squared deviation of each number from its mean. Mathematically it looks something like this:
∑ (x_i - x_avg)² / n.
For a sample (opposed to a population) a division by n - 1 is performed.

Returns:

The variance of the data.

getStandardDeviation

public double getStandardDeviation()

Gets the standard deviation of the data.
The standard deviation is defined as the square root of the variance.

Returns:

The standard deviation of the data.

getSkewness

public double getSkewness()

Computes the skewness (symmetry) of the data.
Click here for more information about skewness in the Wikipedia.

Returns:

The skewness of the data.