org.apache.commons.math4.linear

## Class DiagonalMatrix

• All Implemented Interfaces:
Serializable, AnyMatrix, RealMatrix

public class DiagonalMatrix
extends AbstractRealMatrix
implements Serializable
Implementation of a diagonal matrix.
Since:
3.1.1
Serialized Form
• ### Constructor Summary

Constructors
Constructor and Description
DiagonalMatrix(double[] d)
Creates a matrix using the input array as the underlying data.
DiagonalMatrix(double[] d, boolean copyArray)
Creates a matrix using the input array as the underlying data.
DiagonalMatrix(int dimension)
Creates a matrix with the supplied dimension.
• ### Method Summary

All Methods
Modifier and Type Method and Description
DiagonalMatrix add(DiagonalMatrix m)
Compute the sum of this and m.
void addToEntry(int row, int column, double increment)
Adds (in place) the specified value to the specified entry of this matrix.
RealMatrix copy()
Returns a (deep) copy of this.
RealMatrix createMatrix(int rowDimension, int columnDimension)
Create a new RealMatrix of the same type as the instance with the supplied row and column dimensions.
int getColumnDimension()
Returns the dimension of the domain of this operator.
double[][] getData()
Returns matrix entries as a two-dimensional array.
double[] getDataRef()
Gets a reference to the underlying data array.
double getEntry(int row, int column)
Get the entry in the specified row and column.
int getRowDimension()
Returns the dimension of the codomain of this operator.
DiagonalMatrix inverse()
Computes the inverse of this diagonal matrix.
DiagonalMatrix inverse(double threshold)
Computes the inverse of this diagonal matrix.
boolean isSingular(double threshold)
Returns whether this diagonal matrix is singular, i.e.
DiagonalMatrix multiply(DiagonalMatrix m)
Returns the result of postmultiplying this by m.
RealMatrix multiply(RealMatrix m)
Returns the result of postmultiplying this by m.
void multiplyEntry(int row, int column, double factor)
Multiplies (in place) the specified entry of this matrix by the specified value.
double[] operate(double[] v)
Returns the result of multiplying this by the vector v.
double[] preMultiply(double[] v)
Returns the (row) vector result of premultiplying this by the vector v.
RealVector preMultiply(RealVector v)
Returns the (row) vector result of premultiplying this by the vector v.
void setEntry(int row, int column, double value)
Set the entry in the specified row and column.
DiagonalMatrix subtract(DiagonalMatrix m)
Returns this minus m.
• ### Methods inherited from class org.apache.commons.math4.linear.AbstractRealMatrix

add, copySubMatrix, copySubMatrix, equals, getColumn, getColumnMatrix, getColumnVector, getFrobeniusNorm, getNorm, getRow, getRowMatrix, getRowVector, getSubMatrix, getSubMatrix, getTrace, hashCode, operate, power, preMultiply, scalarAdd, scalarMultiply, setColumn, setColumnMatrix, setColumnVector, setRow, setRowMatrix, setRowVector, setSubMatrix, subtract, toString, transpose, walkInColumnOrder, walkInColumnOrder, walkInColumnOrder, walkInColumnOrder, walkInOptimizedOrder, walkInOptimizedOrder, walkInOptimizedOrder, walkInOptimizedOrder, walkInRowOrder, walkInRowOrder, walkInRowOrder, walkInRowOrder
• ### Methods inherited from class org.apache.commons.math4.linear.RealLinearOperator

isTransposable, operateTranspose
• ### Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait
• ### Methods inherited from interface org.apache.commons.math4.linear.AnyMatrix

canAdd, canMultiply, checkAdd, checkMultiply, isSquare
• ### Constructor Detail

• #### DiagonalMatrix

public DiagonalMatrix(int dimension)
throws NotStrictlyPositiveException
Creates a matrix with the supplied dimension.
Parameters:
dimension - Number of rows and columns in the new matrix.
Throws:
NotStrictlyPositiveException - if the dimension is not positive.
• #### DiagonalMatrix

public DiagonalMatrix(double[] d)
Creates a matrix using the input array as the underlying data.
The input array is copied, not referenced.
Parameters:
d - Data for the new matrix.
• #### DiagonalMatrix

public DiagonalMatrix(double[] d,
boolean copyArray)
throws NullArgumentException
Creates a matrix using the input array as the underlying data.
If an array is created specially in order to be embedded in a this instance and not used directly, the copyArray may be set to false. This will prevent the copying and improve performance as no new array will be built and no data will be copied.
Parameters:
d - Data for new matrix.
copyArray - if true, the input array will be copied, otherwise it will be referenced.
Throws:
NullArgumentException - if d is null
• ### Method Detail

• #### createMatrix

public RealMatrix createMatrix(int rowDimension,
int columnDimension)
throws NotStrictlyPositiveException,
DimensionMismatchException
Create a new RealMatrix of the same type as the instance with the supplied row and column dimensions.
Specified by:
createMatrix in interface RealMatrix
Specified by:
createMatrix in class AbstractRealMatrix
Parameters:
rowDimension - the number of rows in the new matrix
columnDimension - the number of columns in the new matrix
Returns:
a new matrix of the same type as the instance
Throws:
DimensionMismatchException - if the requested dimensions are not equal.
NotStrictlyPositiveException - if row or column dimension is not positive.
• #### copy

public RealMatrix copy()
Returns a (deep) copy of this.
Specified by:
copy in interface RealMatrix
Specified by:
copy in class AbstractRealMatrix
Returns:
matrix copy

public DiagonalMatrix add(DiagonalMatrix m)
throws MatrixDimensionMismatchException
Compute the sum of this and m.
Parameters:
m - Matrix to be added.
Returns:
this + m.
Throws:
MatrixDimensionMismatchException - if m is not the same size as this.
• #### subtract

public DiagonalMatrix subtract(DiagonalMatrix m)
throws MatrixDimensionMismatchException
Returns this minus m.
Parameters:
m - Matrix to be subtracted.
Returns:
this - m
Throws:
MatrixDimensionMismatchException - if m is not the same size as this.
• #### multiply

public DiagonalMatrix multiply(DiagonalMatrix m)
throws DimensionMismatchException
Returns the result of postmultiplying this by m.
Parameters:
m - matrix to postmultiply by
Returns:
this * m
Throws:
DimensionMismatchException - if columnDimension(this) != rowDimension(m)
• #### multiply

public RealMatrix multiply(RealMatrix m)
throws DimensionMismatchException
Returns the result of postmultiplying this by m.
Specified by:
multiply in interface RealMatrix
Overrides:
multiply in class AbstractRealMatrix
Parameters:
m - matrix to postmultiply by
Returns:
this * m
Throws:
DimensionMismatchException - if columnDimension(this) != rowDimension(m)
• #### getData

public double[][] getData()
Returns matrix entries as a two-dimensional array.
Specified by:
getData in interface RealMatrix
Overrides:
getData in class AbstractRealMatrix
Returns:
2-dimensional array of entries
• #### getDataRef

public double[] getDataRef()
Gets a reference to the underlying data array.
Returns:
1-dimensional array of entries.
• #### getEntry

public double getEntry(int row,
int column)
throws OutOfRangeException
Get the entry in the specified row and column. Row and column indices start at 0.
Specified by:
getEntry in interface RealMatrix
Specified by:
getEntry in class AbstractRealMatrix
Parameters:
row - Row index of entry to be fetched.
column - Column index of entry to be fetched.
Returns:
the matrix entry at (row, column).
Throws:
OutOfRangeException - if the row or column index is not valid.
• #### setEntry

public void setEntry(int row,
int column,
double value)
throws OutOfRangeException,
NumberIsTooLargeException
Set the entry in the specified row and column. Row and column indices start at 0.
Specified by:
setEntry in interface RealMatrix
Specified by:
setEntry in class AbstractRealMatrix
Parameters:
row - Row index of entry to be set.
column - Column index of entry to be set.
value - the new value of the entry.
Throws:
NumberIsTooLargeException - if row != column and value is non-zero.
OutOfRangeException - if the row or column index is not valid

public void addToEntry(int row,
int column,
double increment)
throws OutOfRangeException,
NumberIsTooLargeException
Adds (in place) the specified value to the specified entry of this matrix. Row and column indices start at 0.
Specified by:
addToEntry in interface RealMatrix
Overrides:
addToEntry in class AbstractRealMatrix
Parameters:
row - Row index of the entry to be modified.
column - Column index of the entry to be modified.
increment - value to add to the matrix entry.
Throws:
NumberIsTooLargeException - if row != column and increment is non-zero.
OutOfRangeException - if the row or column index is not valid.
• #### multiplyEntry

public void multiplyEntry(int row,
int column,
double factor)
throws OutOfRangeException
Multiplies (in place) the specified entry of this matrix by the specified value. Row and column indices start at 0.
Specified by:
multiplyEntry in interface RealMatrix
Overrides:
multiplyEntry in class AbstractRealMatrix
Parameters:
row - Row index of the entry to be modified.
column - Column index of the entry to be modified.
factor - Multiplication factor for the matrix entry.
Throws:
OutOfRangeException - if the row or column index is not valid.
• #### getRowDimension

public int getRowDimension()
Returns the dimension of the codomain of this operator.
Specified by:
getRowDimension in interface AnyMatrix
Specified by:
getRowDimension in class RealLinearOperator
Returns:
the number of rows of the underlying matrix
• #### getColumnDimension

public int getColumnDimension()
Returns the dimension of the domain of this operator.
Specified by:
getColumnDimension in interface AnyMatrix
Specified by:
getColumnDimension in class RealLinearOperator
Returns:
the number of columns of the underlying matrix
• #### operate

public double[] operate(double[] v)
throws DimensionMismatchException
Returns the result of multiplying this by the vector v.
Specified by:
operate in interface RealMatrix
Overrides:
operate in class AbstractRealMatrix
Parameters:
v - the vector to operate on
Returns:
this * v
Throws:
DimensionMismatchException - if the length of v does not match the column dimension of this.
• #### preMultiply

public double[] preMultiply(double[] v)
throws DimensionMismatchException
Returns the (row) vector result of premultiplying this by the vector v.
Specified by:
preMultiply in interface RealMatrix
Overrides:
preMultiply in class AbstractRealMatrix
Parameters:
v - the row vector to premultiply by
Returns:
v * this
Throws:
DimensionMismatchException - if the length of v does not match the row dimension of this.
• #### preMultiply

public RealVector preMultiply(RealVector v)
throws DimensionMismatchException
Returns the (row) vector result of premultiplying this by the vector v.
Specified by:
preMultiply in interface RealMatrix
Overrides:
preMultiply in class AbstractRealMatrix
Parameters:
v - the row vector to premultiply by
Returns:
v * this
Throws:
DimensionMismatchException - if the dimension of v does not match the row dimension of this.
• #### inverse

public DiagonalMatrix inverse()
throws SingularMatrixException
Computes the inverse of this diagonal matrix.

Note: this method will use a singularity threshold of 0, use inverse(double) if a different threshold is needed.

Returns:
the inverse of m
Throws:
SingularMatrixException - if the matrix is singular
Since:
3.3
• #### inverse

public DiagonalMatrix inverse(double threshold)
throws SingularMatrixException
Computes the inverse of this diagonal matrix.
Parameters:
threshold - Singularity threshold.
Returns:
the inverse of m
Throws:
SingularMatrixException - if the matrix is singular
Since:
3.3
• #### isSingular

public boolean isSingular(double threshold)
Returns whether this diagonal matrix is singular, i.e. any diagonal entry is equal to 0 within the given threshold.
Parameters:
threshold - Singularity threshold.
Returns:
true if the matrix is singular, false otherwise
Since:
3.3