de.lmu.ifi.dbs.elki.math
Class MeanVariance

java.lang.Object
  de.lmu.ifi.dbs.elki.math.MeanVariance

public final class MeanVariance
extends Object

Do some simple statistics (mean, average). This class can repeatedly be fed with data using the add() methods, The resulting values for mean and average can be queried at any time using getMean() and getVariance(). Trivial code, but replicated a lot. The class is final so it should come at low cost.

Author:

Erich Schubert

Field Summary

double	count Number of Samples.
double	sqrSum Sum of Squares
double	sum Sum of values

Constructor Summary

MeanVariance()
Empty constructor

MeanVariance(double sum, double sqrSum, double count)
Constructor from full internal data.

MeanVariance(MeanVariance other)
Constructor from other instance

Method Summary

double	denormalizeValue(double val) Return the unnormalized value (centered at the mean, distance normalized by standard deviation)
double	getCount() Get the number of points the average is based on.
double	getMean() Return mean
double	getStddev() Return standard deviation
double	getVariance() Return variance
static MeanVariance[]	newArray(int dimensionality) Create and initialize a new array of MeanVariance
double	normalizeValue(double val) Return the normalized value (centered at the mean, distance normalized by standard deviation)
void	put(double val) Add a single value with weight 1.0
void	put(double val, double weight) Add data with a given weight
void	put(MeanVariance other) Join the data of another MeanVariance instance.

Methods inherited from class java.lang.Object

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

Field Detail

sum

public double sum

Sum of values

sqrSum

public double sqrSum

Sum of Squares

count

public double count

Number of Samples.

Constructor Detail

MeanVariance

public MeanVariance()

Empty constructor

MeanVariance

public MeanVariance(double sum,
                    double sqrSum,
                    double count)

Constructor from full internal data.

Parameters:

sum - sum

sqrSum - sum of squared values

count - sum of weights

MeanVariance

public MeanVariance(MeanVariance other)

Constructor from other instance

Parameters:

other - other instance to copy data from.

Method Detail

put

public void put(double val,
                double weight)

Add data with a given weight

Parameters:

val - data

weight - weight

put

public void put(double val)

Add a single value with weight 1.0

Parameters:

val - Value

put

public void put(MeanVariance other)

Join the data of another MeanVariance instance.

Parameters:

other -

getCount

public double getCount()

Get the number of points the average is based on.

Returns:

number of data points

getMean

public double getMean()

Return mean

Returns:

mean

getVariance

public double getVariance()

Return variance

Returns:

variance

getStddev

public double getStddev()

Return standard deviation

Returns:

stddev

normalizeValue

public double normalizeValue(double val)

Return the normalized value (centered at the mean, distance normalized by standard deviation)

Parameters:

val - original value

Returns:

normalized value

denormalizeValue

public double denormalizeValue(double val)

Return the unnormalized value (centered at the mean, distance normalized by standard deviation)

Parameters:

val - normalized value

Returns:

de-normalized value

newArray

public static MeanVariance[] newArray(int dimensionality)

Create and initialize a new array of MeanVariance

Parameters:

dimensionality - Dimensionality

Returns:

New and initialized Array