org.apache.commons.math.linear
Interface RealMatrix

All Known Implementing Classes:

RealMatrixImpl

public interface RealMatrix

Interface defining a real-valued matrix with basic algebraic operations.

Matrix element indexing is 0-based -- e.g., getEntry(0, 0) returns the element in the first row, first column of the matrix.

Version:

$Revision: 1.25 $ $Date: 2004/10/12 06:19:50 $

Method Summary

RealMatrix	add(RealMatrix m) Compute the sum of this and m.
RealMatrix	copy() Returns a (deep) copy of this.
double[]	getColumn(int col) Returns the entries in column number col as an array.
int	getColumnDimension() Returns the number of columns in the matrix.
RealMatrix	getColumnMatrix(int column) Returns the entries in column number column as a column matrix.
double[][]	getData() Returns matrix entries as a two-dimensional array.
double	getDeterminant() Returns the determinant of this matrix.
double	getEntry(int row, int column) Returns the entry in the specified row and column.
double	getNorm() Returns the maximum absolute row sum norm of the matrix.
double[]	getRow(int row) Returns the entries in row number row as an array.
int	getRowDimension() Returns the number of rows in the matrix.
RealMatrix	getRowMatrix(int row) Returns the entries in row number row as a row matrix.
RealMatrix	getSubMatrix(int[] selectedRows, int[] selectedColumns) Gets a submatrix.
RealMatrix	getSubMatrix(int startRow, int endRow, int startColumn, int endColumn) Gets a submatrix.
double	getTrace() Returns the trace of the matrix (the sum of the elements on the main diagonal).
RealMatrix	inverse() Returns the inverse of this matrix.
boolean	isSingular() Is this a singular matrix?
boolean	isSquare() Is this a square matrix?
RealMatrix	multiply(RealMatrix m) Returns the result of postmultiplying this by m.
double[]	operate(double[] v) Returns the result of multiplying this by the vector v.
double[]	preMultiply(double[] v) Returns the (row) vector result of premultiplying this by the vector v.
RealMatrix	preMultiply(RealMatrix m) Returns the result premultiplying this by m.
RealMatrix	scalarAdd(double d) Returns the result of adding d to each entry of this.
RealMatrix	scalarMultiply(double d) Returns the result multiplying each entry of this by d.
double[]	solve(double[] b) Returns the solution vector for a linear system with coefficient matrix = this and constant vector = b.
RealMatrix	solve(RealMatrix b) Returns a matrix of (column) solution vectors for linear systems with coefficient matrix = this and constant vectors = columns of b.
RealMatrix	subtract(RealMatrix m) Compute this minus m.
RealMatrix	transpose() Returns the transpose of this matrix.

Method Detail

copy

public RealMatrix copy()

Returns a (deep) copy of this.

Returns:

matrix copy

add

public RealMatrix add(RealMatrix m)
               throws IllegalArgumentException

Compute the sum of this and m.

Parameters:

m - matrix to be added

Returns:

this + m

Throws:

IllegalArgumentException - if m is not the same size as this

subtract

public RealMatrix subtract(RealMatrix m)
                    throws IllegalArgumentException

Compute this minus m.

Parameters:

m - matrix to be subtracted

Returns:

this + m

Throws:

IllegalArgumentException - if m is not the same size as this

scalarAdd

public RealMatrix scalarAdd(double d)

Returns the result of adding d to each entry of this.

Parameters:

d - value to be added to each entry

Returns:

d + this

scalarMultiply

public RealMatrix scalarMultiply(double d)

Returns the result multiplying each entry of this by d.

Parameters:

d - value to multiply all entries by

Returns:

d * this

multiply

public RealMatrix multiply(RealMatrix m)
                    throws IllegalArgumentException

Returns the result of postmultiplying this by m.

Parameters:

m - matrix to postmultiply by

Returns:

this * m

Throws:

IllegalArgumentException - if columnDimension(this) != rowDimension(m)

preMultiply

public RealMatrix preMultiply(RealMatrix m)
                       throws IllegalArgumentException

Returns the result premultiplying this by m.

Parameters:

m - matrix to premultiply by

Returns:

m * this

Throws:

IllegalArgumentException - if rowDimension(this) != columnDimension(m)

getData

public double[][] getData()

Returns matrix entries as a two-dimensional array.

Returns:

2-dimensional array of entries

getNorm

public double getNorm()

Returns the maximum absolute row sum norm of the matrix.

Returns:

norm

getSubMatrix

public RealMatrix getSubMatrix(int startRow,
                               int endRow,
                               int startColumn,
                               int endColumn)
                        throws MatrixIndexException

Gets a submatrix. Rows and columns are indicated counting from 0 to n-1.

Parameters:

startRow - Initial row index

endRow - Final row index

startColumn - Initial column index

endColumn - Final column index

Returns:

The subMatrix containing the data of the specified rows and columns

Throws:

MatrixIndexException - if the indices are not valid

getSubMatrix

public RealMatrix getSubMatrix(int[] selectedRows,
                               int[] selectedColumns)
                        throws MatrixIndexException

Gets a submatrix. Rows and columns are indicated counting from 0 to n-1.

Parameters:

selectedRows - Array of row indices.

selectedColumns - Array of column indices.

Returns:

The subMatrix containing the data in the specified rows and columns

Throws:

MatrixIndexException - if row or column selections are not valid

getRowMatrix

public RealMatrix getRowMatrix(int row)
                        throws MatrixIndexException

Returns the entries in row number row as a row matrix. Row indices start at 0.

Parameters:

row - the row to be fetched

Returns:

row matrix

Throws:

MatrixIndexException - if the specified row index is invalid

getColumnMatrix

public RealMatrix getColumnMatrix(int column)
                           throws MatrixIndexException

Returns the entries in column number column as a column matrix. Column indices start at 0.

Parameters:

column - the column to be fetched

Returns:

column matrix

Throws:

MatrixIndexException - if the specified column index is invalid

getRow

public double[] getRow(int row)
                throws MatrixIndexException

Returns the entries in row number row as an array.

Row indices start at 0. A MatrixIndexException is thrown unless 0 <= row < rowDimension.

Parameters:

row - the row to be fetched

Returns:

array of entries in the row

Throws:

MatrixIndexException - if the specified row index is not valid

getColumn

public double[] getColumn(int col)
                   throws MatrixIndexException

Returns the entries in column number col as an array.

Column indices start at 0. A MatrixIndexException is thrown unless 0 <= column < columnDimension.

Parameters:

col - the column to be fetched

Returns:

array of entries in the column

Throws:

MatrixIndexException - if the specified column index is not valid

getEntry

public double getEntry(int row,
                       int column)
                throws MatrixIndexException

Returns the entry in the specified row and column.

Row and column indices start at 0 and must satisfy

• 0 <= row < rowDimension
• 0 <= column < columnDimension

otherwise a MatrixIndexException is thrown.

Parameters:

row - row location of entry to be fetched

column - column location of entry to be fetched

Returns:

matrix entry in row,column

Throws:

MatrixIndexException - if the row or column index is not valid

transpose

public RealMatrix transpose()

Returns the transpose of this matrix.

Returns:

transpose matrix

inverse

public RealMatrix inverse()
                   throws InvalidMatrixException

Returns the inverse of this matrix.

Returns:

inverse matrix

Throws:

InvalidMatrixException - if this is not invertible

getDeterminant

public double getDeterminant()

Returns the determinant of this matrix.

Returns:

determinant

isSquare

public boolean isSquare()

Is this a square matrix?

Returns:

true if the matrix is square (rowDimension = columnDimension)

isSingular

public boolean isSingular()

Is this a singular matrix?

Returns:

true if the matrix is singular

getRowDimension

public int getRowDimension()

Returns the number of rows in the matrix.

Returns:

rowDimension

getColumnDimension

public int getColumnDimension()

Returns the number of columns in the matrix.

Returns:

columnDimension

getTrace

public double getTrace()

Returns the trace of the matrix (the sum of the elements on the main diagonal).

Returns:

trace

operate

public double[] operate(double[] v)
                 throws IllegalArgumentException

Returns the result of multiplying this by the vector v.

Parameters:

v - the vector to operate on

Returns:

this*v

Throws:

IllegalArgumentException - if columnDimension != v.size()

preMultiply

public double[] preMultiply(double[] v)
                     throws IllegalArgumentException

Returns the (row) vector result of premultiplying this by the vector v.

Parameters:

v - the row vector to premultiply by

Returns:

v*this

Throws:

IllegalArgumentException - if rowDimension != v.size()

solve

public double[] solve(double[] b)
               throws IllegalArgumentException,
                      InvalidMatrixException

Returns the solution vector for a linear system with coefficient matrix = this and constant vector = b.

Parameters:

b - constant vector

Returns:

vector of solution values to AX = b, where A is *this

Throws:

IllegalArgumentException - if this.rowDimension != b.length

InvalidMatrixException - if this matrix is not square or is singular

solve

public RealMatrix solve(RealMatrix b)
                 throws IllegalArgumentException,
                        InvalidMatrixException

Returns a matrix of (column) solution vectors for linear systems with coefficient matrix = this and constant vectors = columns of b.

Parameters:

b - matrix of constant vectors forming RHS of linear systems to to solve

Returns:

matrix of solution vectors

Throws:

IllegalArgumentException - if this.rowDimension != row dimension

InvalidMatrixException - if this matrix is not square or is singular