com.numericalmethod.suanshu.matrix.doubles.operation
Class SubMatrixRef

java.lang.Object
  com.numericalmethod.suanshu.matrix.doubles.operation.SubMatrixRef

All Implemented Interfaces:

DeepCopyable, AbelianGroup<Matrix>, Monoid<Matrix>, Ring<Matrix>, Matrix, MatrixAccessor, MatrixRing, MatrixDimension

public class SubMatrixRef
extends java.lang.Object
implements Matrix

This class creates a 'reference' to a sub-part of a large matrix without copying it. Often, we only need to work on a part of a matrix. We do not want to make copies of a matrix for performance reason.

Example applications include printing a sub-matrix.

The reference sub-matrix is immutable.

Constructor Summary

SubMatrixRef(Matrix A)
Construct a sub-matrix reference.

SubMatrixRef(Matrix A, int rowFrom, int rowTo, int colFrom, int colTo)
Construct a sub-matrix reference.

Method Summary

Matrix	add(Matrix that) this + that
SubMatrixRef	deepCopy() Return 'this' as this Matrix is immutable.
double	get(int row, int col) Get the matrix entry at [row, col].
Vector	getColumn(int col) Get a specified column as a vector.
Vector	getRow(int row) Get a specified row as a vector.
Matrix	minus(Matrix that) this - that
Matrix	multiply(Matrix that) this %*% that
Vector	multiply(Vector v) Right multiply this matrix, A by a vector.
int	nCols() Get the number of columns.
int	nRows() Get the number of rows.
Matrix	ONE() Get an identity matrix that has the same dimension as this matrix.
Matrix	opposite() Get the opposite of this matrix.
Matrix	scaled(double scalar) scalar * this
void	set(int row, int col, double value) Deprecated. SubMatrixRef is immutable
Matrix	t() t(this) Compute the transpose of this matrix.
java.lang.String	toString()
Matrix	ZERO() Get a zero matrix that has the same dimension as this matrix.

Methods inherited from class java.lang.Object

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

Constructor Detail

SubMatrixRef

public SubMatrixRef(Matrix A,
                    int rowFrom,
                    int rowTo,
                    int colFrom,
                    int colTo)

Construct a sub-matrix reference.

Parameters:

A - the matrix to be taken a sub-snapshot from without copying

rowFrom - the beginning row index

rowTo - the ending row index

colFrom - the beginning column index

colTo - the ending column index

Throws:

java.lang.IndexOutOfBoundsException - if rowFrom, rowTo, colFrom, colTo are invalid

SubMatrixRef

public SubMatrixRef(Matrix A)

Construct a sub-matrix reference. This references the whole matrix without copying it.

Parameters:

A - the matrix to be referenced

Method Detail

nRows

public int nRows()

Description copied from interface: MatrixDimension

Get the number of rows. Rows count from 1.

Specified by:

nRows in interface MatrixDimension

Returns:

the number of rows

nCols

public int nCols()

Description copied from interface: MatrixDimension

Get the number of columns. Columns count from 1.

Specified by:

nCols in interface MatrixDimension

Returns:

the number of columns

get

public double get(int row,
                  int col)

Description copied from interface: MatrixAccessor

Get the matrix entry at [row, col].

Specified by:

get in interface MatrixAccessor

Parameters:

row - the row index

col - the column index

Returns:

A[row, col]

getRow

public Vector getRow(int row)

Description copied from interface: MatrixAccessor

Get a specified row as a vector.

Specified by:

getRow in interface MatrixAccessor

Parameters:

row - the row index

Returns:

a vector A[row, ]

getColumn

public Vector getColumn(int col)

Description copied from interface: MatrixAccessor

Get a specified column as a vector.

Specified by:

getColumn in interface MatrixAccessor

Parameters:

col - the column index

Returns:

a vector A[, col]

add

public Matrix add(Matrix that)

Description copied from interface: MatrixRing

this + that

Specified by:

add in interface AbelianGroup<Matrix>

Specified by:

add in interface MatrixRing

Parameters:

that - another matrix

Returns:

the sum of this and that

minus

public Matrix minus(Matrix that)

Description copied from interface: MatrixRing

this - that

Specified by:

minus in interface AbelianGroup<Matrix>

Specified by:

minus in interface MatrixRing

Parameters:

that - another matrix

Returns:

the difference between this and that

multiply

public Matrix multiply(Matrix that)

Description copied from interface: MatrixRing

this %*% that

Specified by:

multiply in interface Monoid<Matrix>

Specified by:

multiply in interface MatrixRing

Parameters:

that - another matrix

Returns:

the product of this and that

multiply

public Vector multiply(Vector v)

Description copied from interface: Matrix

Right multiply this matrix, A by a vector.

Specified by:

multiply in interface Matrix

Parameters:

v - a vector

Returns:

A %*% v

scaled

public Matrix scaled(double scalar)

Description copied from interface: Matrix

scalar * this

Specified by:

scaled in interface Matrix

Parameters:

scalar - a double

Returns:

scalar * this

opposite

public Matrix opposite()

Description copied from interface: MatrixRing

Get the opposite of this matrix.

Specified by:

opposite in interface AbelianGroup<Matrix>

Specified by:

opposite in interface MatrixRing

Returns:

-this

See Also:

Wikipedia: Additive inverse

ZERO

public Matrix ZERO()

Description copied from interface: MatrixRing

Get a zero matrix that has the same dimension as this matrix.

Specified by:

ZERO in interface AbelianGroup<Matrix>

Specified by:

ZERO in interface MatrixRing

Returns:

the 0 matrix

ONE

public Matrix ONE()

Description copied from interface: MatrixRing

Get an identity matrix that has the same dimension as this matrix.

For a non-square matrix, it zeros out the rows (columns) with index > nCols (nRows).

Specified by:

ONE in interface Monoid<Matrix>

Specified by:

ONE in interface MatrixRing

Returns:

an identity matrix

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

t

public Matrix t()

Description copied from interface: MatrixRing

t(this)

Compute the transpose of this matrix. The original matrix does not change. The returned value is independent and can be modified anyhow.

This is the involution on the matrix ring.

Specified by:

t in interface MatrixRing

Returns:

the transpose of this matrix, of the same type

deepCopy

public SubMatrixRef deepCopy()

Return 'this' as this Matrix is immutable. To produce a mutable copy, a deep copy of the referenced matrix is needed.

Specified by:

deepCopy in interface DeepCopyable

Specified by:

deepCopy in interface Matrix

Returns:

'this'

set

@Deprecated
public void set(int row,
                           int col,
                           double value)
         throws MatrixAccessException

Deprecated. SubMatrixRef is immutable

Description copied from interface: MatrixAccessor

Set the matrix entry at [row, col] to value.

This is the only method that may change the entries of a matrix.

Specified by:

set in interface MatrixAccessor

Parameters:

row - the row index

col - the column index

value - the value to set A[row, col] to

Throws:

MatrixAccessException - if row or col is out of range