weka.core
Class Matrix

java.lang.Object
  |
  +--weka.core.Matrix

All Implemented Interfaces:

java.lang.Cloneable, java.io.Serializable

Direct Known Subclasses:

ConfusionMatrix, CostMatrix

public class Matrix

extends java.lang.Object

implements java.lang.Cloneable, java.io.Serializable

Class for performing operations on a matrix of floating-point values. Some of the code is adapted from Numerical Recipes in C.

Author:

Yong Wang (yongwang@cs.waikato.ac.nz), Eibe Frank (eibe@cs.waikato.ac.nz), Len Trigg (eibe@cs.waikato.ac.nz)

See Also:

Serialized Form

Field Summary

protected double[][]

m_Elements The data in the matrix.

Constructor Summary

Matrix(int nr, int nc)
Constructs a matrix.

Matrix(java.io.Reader r)
Reads a matrix from a reader.

Method Summary

Matrix	add(Matrix other) Returns the sum of this matrix with another.
void	addElement(int rowIndex, int columnIndex, double value) Add a value to an element.
java.lang.Object	clone() Creates and returns a clone of this object.
double	getElement(int rowIndex, int columnIndex) Returns the value of a cell in the matrix.
protected void	initialize() Resets the elements to default values (i.e.
void	lubksb(int[] indx, double[] b) Performs LU backward substitution.
int[]	ludcmp() Performs LU decomposition.
static void	main(java.lang.String[] ops) Main method for testing this class.
Matrix	multiply(Matrix b) Reurns the multiplication of two matrices
int	numColumns() Returns the number of columns in the matrix.
int	numRows() Returns the number of rows in the matrix.
double[]	regression(Matrix y) Performs a (ridged) linear regression.
double[]	regression(Matrix y, double[] w) Performs a weighted (ridged) linear regression.
void	setColumn(int index, double[] newColumn) Sets a column of the matrix to the given column.
void	setElement(int rowIndex, int columnIndex, double value) Sets an element of the matrix to the given value.
void	setRow(int index, double[] newRow) Sets a row of the matrix to the given row.
java.lang.String	toString() Converts a matrix to a string
Matrix	transpose() Returns the transpose of a matrix.
void	write(java.io.Writer w) Writes out a matrix

Methods inherited from class java.lang.Object

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

Field Detail

m_Elements

protected double[][] m_Elements

The data in the matrix.

Constructor Detail

Matrix

public Matrix(int nr,
              int nc)

Constructs a matrix.

Parameters:

nr - the number of rows

nc - the number of columns

Matrix

public Matrix(java.io.Reader r)
       throws java.lang.Exception

Reads a matrix from a reader. The first line in the file should contain the number of rows and columns. Subsequent lines contain elements of the matrix.

Parameters:

r - the reader containing the matrix

Throws:

java.lang.Exception - if an error occurs

Method Detail

clone

public java.lang.Object clone()
                       throws java.lang.CloneNotSupportedException

Creates and returns a clone of this object.

Overrides:

clone in class java.lang.Object

Returns:

a clone of this instance.

Throws:

java.lang.CloneNotSupportedException - if an error occurs

write

public void write(java.io.Writer w)
           throws java.lang.Exception

Writes out a matrix

Parameters:

w - the output Writer

Throws:

java.lang.Exception - if an error occurs

initialize

protected void initialize()

Resets the elements to default values (i.e. 0).

getElement

public final double getElement(int rowIndex,
                               int columnIndex)

Returns the value of a cell in the matrix.

Parameters:

rowIndex - the row's index

columnIndex - the column's index

Returns:

the value

addElement

public final void addElement(int rowIndex,
                             int columnIndex,
                             double value)

Add a value to an element.

Parameters:

rowIndex - the row's index.

columnIndex - the column's index.

value - the value to add.

numRows

public final int numRows()

Returns the number of rows in the matrix.

Returns:

the number of rows

numColumns

public final int numColumns()

Returns the number of columns in the matrix.

Returns:

the number of columns

setElement

public final void setElement(int rowIndex,
                             int columnIndex,
                             double value)

Sets an element of the matrix to the given value.

Parameters:

rowIndex - the row's index

columnIndex - the column's index

value - the value

setRow

public final void setRow(int index,
                         double[] newRow)

Sets a row of the matrix to the given row. Performs a deep copy.

Parameters:

index - the row's index

newRow - an array of doubles

setColumn

public final void setColumn(int index,
                            double[] newColumn)

Sets a column of the matrix to the given column. Performs a deep copy.

Parameters:

index - the column's index

newColumn - an array of doubles

toString

public java.lang.String toString()

Converts a matrix to a string

Overrides:

toString in class java.lang.Object

Returns:

the converted string

add

public final Matrix add(Matrix other)

Returns the sum of this matrix with another.

Returns:

the sum.

transpose

public final Matrix transpose()

Returns the transpose of a matrix.

Returns:

the transposition of this instance).

multiply

public final Matrix multiply(Matrix b)

Reurns the multiplication of two matrices

Parameters:

b - the multiplication matrix

Returns:

the product matrix

regression

public final double[] regression(Matrix y)

Performs a (ridged) linear regression.

Parameters:

y - the dependent variable vector

Returns:

the coefficients

Throws:

java.lang.IllegalArgumentException - if not successful

regression

public final double[] regression(Matrix y,
                                 double[] w)

Performs a weighted (ridged) linear regression.

Parameters:

y - the dependent variable vector

w - the array of data point weights

Returns:

the coefficients

Throws:

java.lang.IllegalArgumentException - if the wrong number of weights were provided.

lubksb

public final void lubksb(int[] indx,
                         double[] b)

Performs LU backward substitution. Adapted from Numerical Recipes in C.

Parameters:

indx - the indices of the permutation

b - the double vector, storing constant terms in the equation set; it later stores the computed coefficients' values

ludcmp

public final int[] ludcmp()
                   throws java.lang.Exception

Performs LU decomposition. Adapted from Numerical Recipes in C.

Returns:

the indices of the permutation

Throws:

java.lang.Exception - if the matrix is singular

main

public static void main(java.lang.String[] ops)

Main method for testing this class.