Package dev.nm.algebra.linear.matrix.doubles

Class ImmutableMatrix

java.lang.Object

dev.nm.algebra.linear.matrix.doubles.ImmutableMatrix

All Implemented Interfaces:

Matrix, MatrixAccess, MatrixRing, MatrixTable, AbelianGroup<Matrix>, Monoid<Matrix>, Ring<Matrix>, Table, DeepCopyable

public class ImmutableMatrix
extends Object
implements Matrix

This is a read-only view of a Matrix instance. It keeps a reference to the matrix instance, delegates all operations to the instance except for set(int, int, double) which will always result in an MatrixAccessException. Note that the returned values of all operations (e.g., add()) have the same types as the original matrix. Popular usages of this class include, e.g., the final member of a class, the return value of a method.

Note that the 'immutability' can be broken if the original matrix is modified. To avoid this, make a copy of the original matrix before passing it to the constructor. For example,

 ImmutableMatrix immutable = new ImmutableMatrix(m.deepCopy());
 

Constructor Summary

Constructors

Constructor	Description
ImmutableMatrix(Matrix A)	Construct a read-only version of a matrix.

Method Summary

Modifier and Type	Method	Description
Matrix	add(Matrix that)	this + that
Matrix	deepCopy()	Make a deep copy of the underlying matrix.
boolean	equals(Object obj)
double	get(int i, int j)	Get the matrix entry at [i,j].
Vector	getColumn(int j)	Get the specified column in the matrix as a vector.
Vector	getRow(int i)	Get the specified row in the matrix as a vector.
int	hashCode()
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()	Gets the number of columns.
int	nRows()	Gets 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 c)	Scale this matrix, A, by a constant.
void	set(int row, int col, double value)	Set the matrix entry at [i,j] to a value.
Matrix	t()	Get the transpose of this matrix.
String	toString()
Matrix	ZERO()	Get a zero matrix that has the same dimension as this matrix.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface dev.nm.algebra.linear.matrix.doubles.Matrix

toCSV

Constructor Detail

ImmutableMatrix

public ImmutableMatrix(Matrix A)

Construct a read-only version of a matrix. Note that changing the original matrix changes the "immutable" version as well.

Parameters:

A - a matrix

Method Detail

set

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

Description copied from interface: MatrixAccess

Set the matrix entry at [i,j] to a value. This is the only method that may change a matrix.

Specified by:

set in interface MatrixAccess

Parameters:

row - the row index

col - the column index

value - the value to set A[i,j] to

Throws:

MatrixAccessException - if i or j is out of range

nRows

public int nRows()

Description copied from interface: Table

Gets the number of rows. Rows count from 1.

Specified by:

nRows in interface Table

Returns:

the number of rows

nCols

public int nCols()

Description copied from interface: Table

Gets the number of columns. Columns count from 1.

Specified by:

nCols in interface Table

Returns:

the number of columns

get

public double get(int i,
                  int j)
           throws MatrixAccessException

Description copied from interface: MatrixAccess

Get the matrix entry at [i,j].

Specified by:

get in interface MatrixAccess

Parameters:

i - the row index

j - the column index

Returns:

A[i,j]

Throws:

MatrixAccessException - if i or j is out of range

getRow

public Vector getRow(int i)
              throws MatrixAccessException

Description copied from interface: Matrix

Get the specified row in the matrix as a vector.

Specified by:

getRow in interface Matrix

Parameters:

i - the row index

Returns:

the vector A[i, ]

Throws:

MatrixAccessException - when i < 1, or when i > the number of rows

getColumn

public Vector getColumn(int j)
                 throws MatrixAccessException

Description copied from interface: Matrix

Get the specified column in the matrix as a vector.

Specified by:

getColumn in interface Matrix

Parameters:

j - the column index

Returns:

a vector A[, j]

Throws:

MatrixAccessException - when j < 1, or when j > the number of columns

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 - a 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 - a 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 MatrixRing

Specified by:

multiply in interface Monoid<Matrix>

Parameters:

that - a matrix

Returns:

the product ofthis 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:

Av, a vector

scaled

public Matrix scaled(double c)

Description copied from interface: Matrix

Scale this matrix, A, by a constant.

Specified by:

scaled in interface Matrix

Parameters:

c - a double

Returns:

cA

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 MatrixRing

Specified by:

ONE in interface Monoid<Matrix>

Returns:

an identity matrix

t

public Matrix t()

Description copied from interface: MatrixRing

Get the transpose of this matrix. This is the involution on the matrix ring.

Specified by:

t in interface MatrixRing

Returns:

the transpose of this matrix

deepCopy

public Matrix deepCopy()

Make a deep copy of the underlying matrix. The copy is no longer an ImmutableMatrix and may be mutable.

Specified by:

deepCopy in interface DeepCopyable

Specified by:

deepCopy in interface Matrix

Returns:

a deep copy of the underlying matrix

toString

public String toString()

Overrides:

toString in class Object

equals

public boolean equals(Object obj)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object