# Class Maths

java.lang.Object
weka.core.matrix.Maths
All Implemented Interfaces:
`RevisionHandler`

public class Maths extends Object implements RevisionHandler
Utility class.

Adapted from the JAMA package.

Version:
\$Revision: 5953 \$
Author:
The Mathworks and NIST, Fracpete (fracpete at waikato dot ac dot nz)
• ## Field Summary

Fields
Modifier and Type
Field
Description
`static final int`
`chisqDistribution`
Distribution type: chi-squared
`static final double`
`logPSI`
The constant - log( sqrt(2 pi) )
`static final int`
`normalDistribution`
Distribution type: noraml
`static final double`
`PSI`
The constant 1 / sqrt(2 pi)
`static final int`
`undefinedDistribution`
Distribution type: undefined
• ## Constructor Summary

Constructors
Constructor
Description
`Maths()`

• ## Method Summary

Modifier and Type
Method
Description
`static double`
`dchisq(double x)`
Returns the density of the Chi-squared distribution.
`static double`
```dchisq(double x, double ncp)```
Returns the density of the noncentral Chi-squared distribution.
`static DoubleVector`
```dchisq(double x, DoubleVector ncp)```
Returns the density of the noncentral Chi-squared distribution.
`static double`
`dchisqLog(double x)`
Returns the log-density of the noncentral Chi-square distribution.
`static double`
```dchisqLog(double x, double ncp)```
Returns the log-density value of a noncentral Chi-square distribution.
`static DoubleVector`
```dchisqLog(double x, DoubleVector ncp)```
Returns the log-density of a set of noncentral Chi-squared distributions.
`static double`
`dnorm(double x)`
Returns the density of the standard normal.
`static double`
```dnorm(double x, double mean, double sd)```
Returns the density value of a standard normal.
`static DoubleVector`
```dnorm(double x, DoubleVector mean, double sd)```
Returns the density values of a set of normal distributions with different means.
`static double`
`dnormLog(double x)`
Returns the log-density of the standard normal.
`static double`
```dnormLog(double x, double mean, double sd)```
Returns the log-density value of a standard normal.
`static DoubleVector`
```dnormLog(double x, DoubleVector mean, double sd)```
Returns the log-density values of a set of normal distributions with different means.
`String`
`getRevision()`
Returns the revision string.
`static double`
```hypot(double a, double b)```
sqrt(a^2 + b^2) without under/overflow.
`static double`
`pchisq(double x)`
Returns the cumulative probability of the Chi-squared distribution
`static double`
```pchisq(double x, double ncp)```
Returns the cumulative probability of the noncentral Chi-squared distribution.
`static DoubleVector`
```pchisq(double x, DoubleVector ncp)```
Returns the cumulative probability of a set of noncentral Chi-squared distributions.
`static double`
`pnorm(double x)`
Returns the cumulative probability of the standard normal.
`static double`
```pnorm(double x, double mean, double sd)```
Returns the cumulative probability of a normal distribution.
`static DoubleVector`
```pnorm(double x, DoubleVector mean, double sd)```
Returns the cumulative probability of a set of normal distributions with different means.
`static DoubleVector`
```rchisq(int n, double ncp, Random random)```
Generates a sample of a Chi-square distribution.
`static DoubleVector`
```rnorm(int n, double mean, double sd, Random random)```
Generates a sample of a normal distribution.
`static double`
`square(double x)`
Returns the square of a value

### Methods inherited from class java.lang.Object

`equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`
• ## Field Details

• ### PSI

public static final double PSI
The constant 1 / sqrt(2 pi)
• ### logPSI

public static final double logPSI
The constant - log( sqrt(2 pi) )
• ### undefinedDistribution

public static final int undefinedDistribution
Distribution type: undefined
• ### normalDistribution

public static final int normalDistribution
Distribution type: noraml
• ### chisqDistribution

public static final int chisqDistribution
Distribution type: chi-squared
• ## Constructor Details

• ### Maths

public Maths()
• ## Method Details

• ### hypot

public static double hypot(double a, double b)
sqrt(a^2 + b^2) without under/overflow.
• ### square

public static double square(double x)
Returns the square of a value
Parameters:
`x` -
Returns:
the square
• ### pnorm

public static double pnorm(double x)
Returns the cumulative probability of the standard normal.
Parameters:
`x` - the quantile
• ### pnorm

public static double pnorm(double x, double mean, double sd)
Returns the cumulative probability of a normal distribution.
Parameters:
`x` - the quantile
`mean` - the mean of the normal distribution
`sd` - the standard deviation of the normal distribution.
• ### pnorm

public static DoubleVector pnorm(double x, DoubleVector mean, double sd)
Returns the cumulative probability of a set of normal distributions with different means.
Parameters:
`x` - the vector of quantiles
`mean` - the means of the normal distributions
`sd` - the standard deviation of the normal distribution.
Returns:
the cumulative probability
• ### dnorm

public static double dnorm(double x)
Returns the density of the standard normal.
Parameters:
`x` - the quantile
Returns:
the density
• ### dnorm

public static double dnorm(double x, double mean, double sd)
Returns the density value of a standard normal.
Parameters:
`x` - the quantile
`mean` - the mean of the normal distribution
`sd` - the standard deviation of the normal distribution.
Returns:
the density
• ### dnorm

public static DoubleVector dnorm(double x, DoubleVector mean, double sd)
Returns the density values of a set of normal distributions with different means.
Parameters:
`x` - the quantile
`mean` - the means of the normal distributions
`sd` - the standard deviation of the normal distribution.
Returns:
the density
• ### dnormLog

public static double dnormLog(double x)
Returns the log-density of the standard normal.
Parameters:
`x` - the quantile
Returns:
the density
• ### dnormLog

public static double dnormLog(double x, double mean, double sd)
Returns the log-density value of a standard normal.
Parameters:
`x` - the quantile
`mean` - the mean of the normal distribution
`sd` - the standard deviation of the normal distribution.
Returns:
the density
• ### dnormLog

public static DoubleVector dnormLog(double x, DoubleVector mean, double sd)
Returns the log-density values of a set of normal distributions with different means.
Parameters:
`x` - the quantile
`mean` - the means of the normal distributions
`sd` - the standard deviation of the normal distribution.
Returns:
the density
• ### rnorm

public static DoubleVector rnorm(int n, double mean, double sd, Random random)
Generates a sample of a normal distribution.
Parameters:
`n` - the size of the sample
`mean` - the mean of the normal distribution
`sd` - the standard deviation of the normal distribution.
`random` - the random stream
Returns:
the sample
• ### pchisq

public static double pchisq(double x)
Returns the cumulative probability of the Chi-squared distribution
Parameters:
`x` - the quantile
• ### pchisq

public static double pchisq(double x, double ncp)
Returns the cumulative probability of the noncentral Chi-squared distribution.
Parameters:
`x` - the quantile
`ncp` - the noncentral parameter
• ### pchisq

public static DoubleVector pchisq(double x, DoubleVector ncp)
Returns the cumulative probability of a set of noncentral Chi-squared distributions.
Parameters:
`x` - the quantile
`ncp` - the noncentral parameters
• ### dchisq

public static double dchisq(double x)
Returns the density of the Chi-squared distribution.
Parameters:
`x` - the quantile
Returns:
the density
• ### dchisq

public static double dchisq(double x, double ncp)
Returns the density of the noncentral Chi-squared distribution.
Parameters:
`x` - the quantile
`ncp` - the noncentral parameter
• ### dchisq

public static DoubleVector dchisq(double x, DoubleVector ncp)
Returns the density of the noncentral Chi-squared distribution.
Parameters:
`x` - the quantile
`ncp` - the noncentral parameters
• ### dchisqLog

public static double dchisqLog(double x)
Returns the log-density of the noncentral Chi-square distribution.
Parameters:
`x` - the quantile
Returns:
the density
• ### dchisqLog

public static double dchisqLog(double x, double ncp)
Returns the log-density value of a noncentral Chi-square distribution.
Parameters:
`x` - the quantile
`ncp` - the noncentral parameter
Returns:
the density
• ### dchisqLog

public static DoubleVector dchisqLog(double x, DoubleVector ncp)
Returns the log-density of a set of noncentral Chi-squared distributions.
Parameters:
`x` - the quantile
`ncp` - the noncentral parameters
• ### rchisq

public static DoubleVector rchisq(int n, double ncp, Random random)
Generates a sample of a Chi-square distribution.
Parameters:
`n` - the size of the sample
`ncp` - the noncentral parameter
`random` - the random stream
Returns:
the sample
• ### getRevision

public String getRevision()
Returns the revision string.
Specified by:
`getRevision` in interface `RevisionHandler`
Returns:
the revision