com.numericalmethod.suanshu.matrix.doubles.matrixtype.dense.triangle
Class LowerTriangularMatrix

java.lang.Object
  com.numericalmethod.suanshu.matrix.doubles.matrixtype.dense.triangle.LowerTriangularMatrix

All Implemented Interfaces:

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

Direct Known Subclasses:

CholeskyWang2006

public class LowerTriangularMatrix
extends java.lang.Object
implements Matrix, Densifiable

A lower triangular matrix has 0 entries where column index > row index. A lower triangular matrix is always square.

Constructor Summary

LowerTriangularMatrix(double[][] data)
Construct a lower triangular matrix from a 2D double[][] array.

LowerTriangularMatrix(int dim)
Construct a lower triangular matrix of dimension dim * dim.

LowerTriangularMatrix(LowerTriangularMatrix L)
Copy constructor.

LowerTriangularMatrix(Matrix A)
Construct a lower triangular matrix from a matrix.

Method Summary

Matrix	add(Matrix that) this + that
LowerTriangularMatrix	deepCopy() The implementation returns an instance created from this by the copy constructor of the class, or just this if the instance itself is immutable.
boolean	equals(java.lang.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() Get the number of columns.
int	nRows() Get the number of rows.
LowerTriangularMatrix	ONE() Get an identity matrix that has the same dimension as this matrix.
LowerTriangularMatrix	opposite() Get the opposite of this matrix.
LowerTriangularMatrix	scaled(double scalar) Scale this matrix, A, by a constant.
void	set(int i, int j, double value) Set the matrix entry at [i,j] to a value.
UpperTriangularMatrix	t() t(A)
DenseMatrix	toDense() Densify a matrix, i.e., convert a matrix implementation to the standard dense matrix, DenseMatrix.
java.lang.String	toString()
LowerTriangularMatrix	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

Constructor Detail

LowerTriangularMatrix

public LowerTriangularMatrix(int dim)

Construct a lower triangular matrix of dimension dim * dim.

Parameters:

dim - the matrix dimension

LowerTriangularMatrix

public LowerTriangularMatrix(double[][] data)

Construct a lower triangular matrix from a 2D double[][] array.

Parameters:

data - the 2D array input

Throws:

java.lang.IllegalArgumentException - when the input data is not a lower triangular

LowerTriangularMatrix

public LowerTriangularMatrix(Matrix A)

Construct a lower triangular matrix from a matrix.

Parameters:

A - a matrix

Throws:

java.lang.IllegalArgumentException - when A is not square

LowerTriangularMatrix

public LowerTriangularMatrix(LowerTriangularMatrix L)

Copy constructor.

Parameters:

L - a lower triangular matrix

Method Detail

deepCopy

public LowerTriangularMatrix deepCopy()

Description copied from interface: DeepCopyable

The implementation returns an instance created from this by the copy constructor of the class, or just this if the instance itself is immutable.

Specified by:

deepCopy in interface DeepCopyable

Specified by:

deepCopy in interface Matrix

Returns:

an independent (deep) copy of the instance

toDense

public DenseMatrix toDense()

Description copied from interface: Densifiable

Densify a matrix, i.e., convert a matrix implementation to the standard dense matrix, DenseMatrix.

Specified by:

toDense in interface Densifiable

Returns:

a matrix representation in DenseMatrix

nRows

public int nRows()

Description copied from interface: Table

Get 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

Get the number of columns. Columns count from 1.

Specified by:

nCols in interface Table

Returns:

the number of columns

set

public void set(int i,
                int j,
                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:

i - the row index

j - the column index

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

Throws:

MatrixAccessException - if i or j is out of range

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)

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, ]

getColumn

public Vector getColumn(int j)

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]

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 Monoid<Matrix>

Specified by:

multiply in interface MatrixRing

Parameters:

that - a matrix

Returns:

the product ofthis and that

t

public UpperTriangularMatrix t()

t(A)

Specified by:

t in interface MatrixRing

Returns:

an upper triangular matrix which is the transpose of this

scaled

public LowerTriangularMatrix scaled(double scalar)

Description copied from interface: Matrix

Scale this matrix, A, by a constant.

Specified by:

scaled in interface Matrix

Parameters:

scalar - a double

Returns:

cA

opposite

public LowerTriangularMatrix 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

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

ZERO

public LowerTriangularMatrix 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 LowerTriangularMatrix 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

equals

public boolean equals(java.lang.Object obj)

Overrides:

equals in class java.lang.Object

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object