weka.core.matrix

## Class Maths

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

```public class Maths
extends java.lang.Object
implements RevisionHandler```
Utility class.

Version:
\$Revision: 1.3 \$
Author:
The Mathworks and NIST, Fracpete (fracpete at waikato dot ac dot nz)
• ### Field Summary

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

Constructors
Constructor and Description
`Maths()`
• ### Method Summary

All Methods
Modifier and Type Method and 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.
`java.lang.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, java.util.Random random)```
Generates a sample of a Chi-square distribution.
`static DoubleVector` ```rnorm(int n, double mean, double sd, java.util.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 Detail

• #### PSI

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

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

`public static final int undefinedDistribution`
Distribution type: undefined
Constant Field Values
• #### normalDistribution

`public static final int normalDistribution`
Distribution type: noraml
Constant Field Values
• #### chisqDistribution

`public static final int chisqDistribution`
Distribution type: chi-squared
Constant Field Values
• ### Constructor Detail

• #### Maths

`public Maths()`
• ### Method Detail

• #### 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,
java.util.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,
java.util.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 java.lang.String getRevision()`
Returns the revision string.
Specified by:
`getRevision` in interface `RevisionHandler`
Returns:
the revision