# SuanShu, a Java numerical and statistical library

com.numericalmethod.suanshu.algebra.linear.matrix.doubles.matrixtype.dense.triangle

## Class LowerTriangularMatrix

• java.lang.Object
• com.numericalmethod.suanshu.algebra.linear.matrix.doubles.matrixtype.dense.triangle.LowerTriangularMatrix
• ### Constructor Summary

Constructors
Constructor and Description
LowerTriangularMatrix(double[][] data)
Constructs a lower triangular matrix from a 2D double[][] array.
LowerTriangularMatrix(int dim)
Constructs a lower triangular matrix of dimension dim * dim.
LowerTriangularMatrix(LowerTriangularMatrix L)
Copy constructor.
LowerTriangularMatrix(Matrix A)
Constructs a lower triangular matrix from a matrix.
• ### Method Summary

All Methods
Modifier and Type Method and Description
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(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.
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.
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)
Constructs a lower triangular matrix of dimension dim * dim.
Parameters:
dim - the matrix dimension
• #### LowerTriangularMatrix

public LowerTriangularMatrix(double[][] data)
Constructs a lower triangular matrix from a 2D double[][] array.
Parameters:
data - the 2D array input
Throws:
IllegalArgumentException - when the input data is not a lower triangular
• #### LowerTriangularMatrix

public LowerTriangularMatrix(Matrix A)
Constructs a lower triangular matrix from a matrix.
Parameters:
A - a matrix
Throws:
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 Matrix
Specified by:
deepCopy in interface DeepCopyable
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
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
• #### 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]

public Matrix add(Matrix that)
Description copied from interface: MatrixRing
this + that
Specified by:
add in interface MatrixRing
Specified by:
add in interface AbelianGroup<Matrix>
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 MatrixRing
Specified by:
minus in interface AbelianGroup<Matrix>
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
• #### 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 MatrixRing
Specified by:
opposite in interface AbelianGroup<Matrix>
Returns:
-this
• #### 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 MatrixRing
Specified by:
ZERO in interface AbelianGroup<Matrix>
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 MatrixRing
Specified by:
ONE in interface Monoid<Matrix>
Returns:
an identity 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