com.numericalmethod.suanshu.matrix.doubles.matrixtype.dense.diagonal
Class TridiagonalMatrix

java.lang.Object
  com.numericalmethod.suanshu.matrix.doubles.matrixtype.MatrixMathImpl<T>
      com.numericalmethod.suanshu.matrix.doubles.matrixtype.MatrixStorageImpl<T>
          com.numericalmethod.suanshu.matrix.doubles.matrixtype.dense.diagonal.TridiagonalMatrix

All Implemented Interfaces:

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

public class TridiagonalMatrix
extends MatrixStorageImpl<T>

This class represents a matrix with non-zero entries only on the super, main and sub diagonals.

See Also:

Wikipedia: Tridiagonal matrix

Constructor Summary

TridiagonalMatrix(double[][] data)
Construct a tridiagonal matrix from a 2D double[][] array.

TridiagonalMatrix(int dim)
Construct a tridiagonal matrix of dimension dim * dim.

TridiagonalMatrix(TridiagonalMatrix that)
Copy constructor performing a deep copy.

Method Summary

TridiagonalMatrix	add(TridiagonalMatrix that)
TridiagonalMatrix	deepCopy() The implementation can return an instance created from this by the copy constructor of the class, or just this if the instance itself is immutable.
DenseVector	diagonal() Get a copy of the diagonal of the matrix.
boolean	equals(java.lang.Object obj) Check if two matrices (of different implementations) are equal.
DenseVector	getColumn(int col) Get a specified column as a vector.
DenseVector	getRow(int row) Get a specified row as a vector.
int	hashCode()
TridiagonalMatrix	minus(TridiagonalMatrix that)
TridiagonalMatrix	ONE() Get an identity matrix that has the same dimension as this matrix.
TridiagonalMatrix	scaled(double scalar) scalar * this
DenseVector	subDiagonal() Get a copy of the sub-diagonal of the matrix.
DenseVector	superDiagonal() Get a copy of the super-diagonal of the matrix.
TridiagonalMatrix	t() t(this) Compute the transpose of this matrix.
DenseMatrix	toDense() Densify a matrix, i.e., convert a matrix implementation to a standard dense matrix, DenseMatrix.
java.lang.String	toString()
TridiagonalMatrix	ZERO() The additive element 0 in the group, such that for all elements a in the group, the equation 0 + a = a + 0 = a holds.

Methods inherited from class com.numericalmethod.suanshu.matrix.doubles.matrixtype.MatrixStorageImpl

get, getMatrixData, set, setMatrixData

Methods inherited from class com.numericalmethod.suanshu.matrix.doubles.matrixtype.MatrixMathImpl

add, call, getSample, minus, multiply, multiply, nCols, nRows, opposite, setColumn, setColumn, setRow, setRow

Methods inherited from class java.lang.Object

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

Constructor Detail

TridiagonalMatrix

public TridiagonalMatrix(int dim)

Construct a tridiagonal matrix of dimension dim * dim.

Parameters:

dim - dimension of the matrix

TridiagonalMatrix

public TridiagonalMatrix(double[][] data)

Construct a tridiagonal matrix from a 2D double[][] array.

1. the first row is the super diagonal; (dim - 1) entries
2. the second row is the main diagonal; (dim) entries
3. the third row is the sub diagonal; (dim - 1) entries

For example,

         new double[][]{
              {2, 5, 8, 11},
              {1, 4, 7, 10, 13},
              {3, 6, 9, 12}
          }
 

is

              | 1  2  0  0   0  |
              | 3  4  5  0   0  |
              | 0  6  7  8   0  |
              | 0  0  9  10  11 |
              | 0  0  0  12  13 |
 

We allow 'null' input when a diagonal is 0s.

For example,

         new double[][]{
              {2, 5, 8, 11},
              {1, 4, 7, 10, 13},
              null
          }
 

is

              | 1  2  0  0   0  |
              | 0  4  5  0   0  |
              | 0  0  7  8   0  |
              | 0  0  0  10  11 |
              | 0  0  0  0   13 |
 

The following is not allowed because the dimension cannot be determined.

         new double[][]{
              null,
              null,
              null
          }
 

Parameters:

data - the 2D array input

TridiagonalMatrix

public TridiagonalMatrix(TridiagonalMatrix that)

Copy constructor performing a deep copy.

Parameters:

that - a TridiagonalMatrix

Method Detail

deepCopy

public TridiagonalMatrix deepCopy()

Description copied from interface: Matrix

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

Override the return type.

Returns:

an independent copy of Matrix instance

add

public TridiagonalMatrix add(TridiagonalMatrix that)

minus

public TridiagonalMatrix minus(TridiagonalMatrix that)

ZERO

public TridiagonalMatrix ZERO()

Description copied from interface: AbelianGroup

The additive element 0 in the group, such that for all elements a in the group, the equation

0 + a = a + 0 = a

holds.

Returns:

0

ONE

public TridiagonalMatrix 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).

Returns:

an identity matrix

t

public TridiagonalMatrix 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

Overrides:

t in class MatrixMathImpl<TridiagonalMatrix>

Returns:

the transpose of this matrix, of the same type

scaled

public TridiagonalMatrix scaled(double scalar)

Description copied from interface: Matrix

scalar * this

Specified by:

scaled in interface Matrix

Overrides:

scaled in class MatrixMathImpl<TridiagonalMatrix>

Parameters:

scalar - a double

Returns:

scalar * this

toDense

public DenseMatrix toDense()

Description copied from interface: Densifiable

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

This is equivalent to

new DenseMatrix(Matrix A)

Individual matrix implementation may optimize the conversion by taking advantage of having access to the class' private members. In other words, toDense() is in general more efficient than explicit copy construction.

As an example, for some long matrix computations, we may not be sure about the return type. We can always cast it to the standard matrix. That is,

DenseMatrix A = B.multiply(C).add(D).minus(E).toDense();

This statement always works regardless of the types of B, C, D, and E.

Specified by:

toDense in interface Densifiable

Returns:

a matrix representation in DenseMatrix

diagonal

public DenseVector diagonal()

Get a copy of the diagonal of the matrix.

Returns:

a copy of the diagonal

superDiagonal

public DenseVector superDiagonal()

Get a copy of the super-diagonal of the matrix.

Returns:

a copy of the super-diagonal

subDiagonal

public DenseVector subDiagonal()

Get a copy of the sub-diagonal of the matrix.

Returns:

a copy of the sub-diagonal

getRow

public DenseVector getRow(int row)

Description copied from interface: MatrixAccessor

Get a specified row as a vector.

Specified by:

getRow in interface MatrixAccessor

Overrides:

getRow in class MatrixMathImpl<T extends com.numericalmethod.suanshu.matrix.doubles.matrixtype.dense.diagonal.DiagonalDataMatrix>

Parameters:

row - the row index

Returns:

a vector A[row, ]

getColumn

public DenseVector getColumn(int col)

Description copied from interface: MatrixAccessor

Get a specified column as a vector.

Specified by:

getColumn in interface MatrixAccessor

Overrides:

getColumn in class MatrixMathImpl<T extends com.numericalmethod.suanshu.matrix.doubles.matrixtype.dense.diagonal.DiagonalDataMatrix>

Parameters:

col - the column index

Returns:

a vector A[, col]

toString

public java.lang.String toString()

Overrides:

toString in class MatrixMathImpl<T extends com.numericalmethod.suanshu.matrix.doubles.matrixtype.dense.diagonal.DiagonalDataMatrix>

equals

public boolean equals(java.lang.Object obj)

Description copied from class: MatrixStorageImpl

Check if two matrices (of different implementations) are equal. They are equal iff two matrices have the same values, entry-by-entry.

Overrides:

equals in class MatrixStorageImpl<T extends com.numericalmethod.suanshu.matrix.doubles.matrixtype.dense.diagonal.DiagonalDataMatrix>

Returns:

true iff two matrices have the same values, entry-by-entry

hashCode

public int hashCode()

Overrides:

hashCode in class MatrixStorageImpl<T extends com.numericalmethod.suanshu.matrix.doubles.matrixtype.dense.diagonal.DiagonalDataMatrix>