Package org.djunits.vecmat.d2

Class Matrix2x2<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>>

java.lang.Object

org.djunits.vecmat.def.VectorMatrix<Q,U,M,SI,H>

org.djunits.vecmat.def.Matrix<Q,U,M,SI,H>

org.djunits.vecmat.def.SquareMatrix<Q,U,M,SI,H>

org.djunits.vecmat.def.SquareDenseMatrix<Q,U,Matrix2x2<Q,U>,Matrix2x2<SIQuantity,SIUnit>,Matrix2x2<?,?>>

org.djunits.vecmat.d2.Matrix2x2<Q,U>

Type Parameters:

Q - the quantity type

U - the unit type

All Implemented Interfaces:

Serializable, Additive<Matrix2x2<Q,U>>, Scalable<Matrix2x2<Q,U>>, Value<U,Matrix2x2<Q,U>>, Hadamard<Matrix2x2<?,?>,Matrix2x2<SIQuantity,SIUnit>>

public class Matrix2x2<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>>
extends SquareDenseMatrix<Q,U,Matrix2x2<Q,U>,Matrix2x2<SIQuantity,SIUnit>,Matrix2x2<?,?>>

Matrix2x2 implements a matrix with 2x2 real-valued entries. The matrix is immutable, except for the display unit, which can be changed.

Copyright (c) 2025-2026 Delft University of Technology, Jaffalaan 5, 2628 BX Delft, the Netherlands. All rights reserved. See for project information https://djunits.org. The DJUNITS project is distributed under a three-clause BSD-style license.

Author:

Alexander Verbraeck

See Also:

• Serialized Form

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	Matrix2x2(double[] arrayInUnit, U displayUnit)	Create a new Matrix2x2 with a unit.

Method Summary

Modifier and Type	Method	Description
Matrix2x2<SIQuantity,SIUnit>	adjugate()	Return the adjugate (classical adjoint) matrix for this matrix, often denoted as adj(M).
<TQ extends Quantity<TQ, TU>, TU extends UnitInterface<TU, TQ>> Matrix2x2<TQ,TU>	as(TU targetUnit)	Return the matrix 'as' a matrix with a known quantity, using a unit to express the result in.
Matrix2x2<SIQuantity,SIUnit>	divideElements(Matrix2x2<?,?> other)	Divide the elements of this vector, matrix or table on an element-by-element basis with those of another collection of the same type (but possibly representing another quantity).
Vector2.Col<Q,U>	getColumnVector(int col)	Return a quantity column (0-based) from the vector or matrix.
Vector2.Col<Q,U>	getDiagonalVector()	Retrieve the main diagonal of the matrix as a column vector.
Vector2.Row<Q,U>	getRowVector(int row)	Return a quantity row (0-based) from the vector or matrix.
Matrix2x2<Q,U>	instantiateSi(double[] siNew)	Return a new vector or matrix with the given SI or BASE values.
Matrix2x2<SIQuantity,SIUnit>	instantiateSi(double[] siNew, SIUnit siUnit)	Return a new vector or matrix in SI-units with the given SI or BASE values.
Matrix2x2<SIQuantity,SIUnit>	inverse()	Return the inverse of the square matrix, if the matrix is non-singular.
Matrix2x2<SIQuantity,SIUnit>	invertElements()	Invert the vector, matrix or table on an element-by-element basis.
Vector2.Col<Q,U>	mgetColumnVector(int mCol)	Return a quantity column (1-based) from the vector or matrix.
Vector2.Row<Q,U>	mgetRowVector(int mRow)	Return a quantity row (1-based) from the vector or matrix.
Matrix2x2<SIQuantity,SIUnit>	multiply(Matrix2x2<?,?> otherMat)	Multiply this matrix with another matrix using matrix multiplication and return the result.
Vector2.Col<SIQuantity,SIUnit>	multiply(Vector2.Col<?,?> otherVec)	Multiply this matrix with a column vector, resulting in a column vector.
Matrix2x2<SIQuantity,SIUnit>	multiplyElements(Quantity<?,?> quantity)	Multiply the elements of this vector, matrix or table by the given quantity.
Matrix2x2<SIQuantity,SIUnit>	multiplyElements(Matrix2x2<?,?> other)	Multiply the elements of this vector, matrix or table on an element-by-element basis with those of another collection of the same type (but possibly representing another quantity).
static <Q extends Quantity<Q, U>, U extends UnitInterface<U, Q>> Matrix2x2<Q,U>	of(double[][] gridInUnit, U displayUnit)	Create a new Matrix2x2 with a unit, based on a 2-dimensional grid.
static <Q extends Quantity<Q, U>, U extends UnitInterface<U, Q>> Matrix2x2<Q,U>	of(double[] arrayInUnit, U displayUnit)	Create a new Matrix2x2 with a unit, based on a 1-dimensional array.

Methods inherited from class org.djunits.vecmat.def.SquareDenseMatrix

cols, equals, getColumnSi, getRowSi, hashCode, rows, si, si

Methods inherited from class org.djunits.vecmat.def.SquareMatrix

determinant, determinantScalar, getDiagonalScalars, getDiagonalSi, isSkewSymmetric, isSkewSymmetric, isSymmetric, isSymmetric, normFrobenius, order, trace, transpose

Methods inherited from class org.djunits.vecmat.def.Matrix

checkMultiply, checkMultiply, multiply

Methods inherited from class org.djunits.vecmat.def.VectorMatrix

abs, add, add, asMatrixNxM, asQuantityTable, checkCol, checkRow, divideElements, get, getColumnScalars, getDisplayUnit, getRowScalars, getScalarGrid, isRelative, max, mcheckCol, mcheckRow, mean, median, mget, mgetColumnScalars, mgetColumnSi, mgetRowScalars, mgetRowSi, min, mode, msi, multiplyElements, negate, scaleBy, setDisplayUnit, subtract, subtract, sum, toString, toString

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.djunits.vecmat.operations.Hadamard

divideElements

Methods inherited from interface org.djunits.value.Scalable

divideBy

Methods inherited from interface org.djunits.value.Value

isAbsolute, setDisplayUnit

Constructor Details

Matrix2x2

protected Matrix2x2(double[] arrayInUnit,
 U displayUnit)

Create a new Matrix2x2 with a unit.

Parameters:

arrayInUnit - the matrix values {a11, a12, a21, a22} expressed in the displayUnit

displayUnit - the display unit to use

Method Details

of

public static <Q extends Quantity<Q,
U>,
U extends UnitInterface<U,
Q>>
Matrix2x2<Q,U> of(double[] arrayInUnit,
 U displayUnit)

Create a new Matrix2x2 with a unit, based on a 1-dimensional array.

Implementation Note: the condition is also checked by super() but the fail fast approach is used here

Type Parameters:

Q - the quantity type

U - the unit type

Parameters:

arrayInUnit - the matrix values {a11, a12, a21, a22} expressed in the display unit

displayUnit - the display unit to use

Returns:

a new Matrix2x2 with a unit

Throws:

IllegalArgumentException - when valueArray does not contain 2x2 = 4 values

of

public static <Q extends Quantity<Q,
U>,
U extends UnitInterface<U,
Q>>
Matrix2x2<Q,U> of(double[][] gridInUnit,
 U displayUnit)

Create a new Matrix2x2 with a unit, based on a 2-dimensional grid.

Type Parameters:

Q - the quantity type

U - the unit type

Parameters:

gridInUnit - the matrix values {{a11, a12}, {a21, a22}} expressed in the display unit

displayUnit - the display unit to use

Returns:

a new Matrix2x2 with a unit

instantiateSi

public Matrix2x2<Q,U> instantiateSi(double[] siNew)

Description copied from class: VectorMatrix

Return a new vector or matrix with the given SI or BASE values.

Specified by:

instantiateSi in class VectorMatrix<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>,Matrix2x2<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>>,Matrix2x2<SIQuantity,SIUnit>,Matrix2x2<?,?>>

Parameters:

siNew - the values for the new vector or matrix in row-major format

Returns:

a new matrix with the provided SI or BASE values

instantiateSi

public Matrix2x2<SIQuantity,SIUnit> instantiateSi(double[] siNew,
 SIUnit siUnit)

Description copied from class: VectorMatrix

Return a new vector or matrix in SI-units with the given SI or BASE values.

Specified by:

instantiateSi in class VectorMatrix<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>,Matrix2x2<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>>,Matrix2x2<SIQuantity,SIUnit>,Matrix2x2<?,?>>

Parameters:

siNew - the values for the new vector or matrix in row-major format

siUnit - the new unit for the new vector or matrix

Returns:

a new matrix with the provided SI or BASE values

getRowVector

public Vector2.Row<Q,U> getRowVector(int row)

Description copied from class: VectorMatrix

Return a quantity row (0-based) from the vector or matrix. Note that the specific vector to return can be tightened by the implementing class.

Specified by:

getRowVector in class VectorMatrix<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>,Matrix2x2<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>>,Matrix2x2<SIQuantity,SIUnit>,Matrix2x2<?,?>>

Parameters:

row - the row number to retrieve (0-based)

Returns:

a row vector with the data at the given row

mgetRowVector

public Vector2.Row<Q,U> mgetRowVector(int mRow)

Description copied from class: VectorMatrix

Return a quantity row (1-based) from the vector or matrix. Note that the specific vector to return can be tightened by the implementing class.

Specified by:

mgetRowVector in class VectorMatrix<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>,Matrix2x2<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>>,Matrix2x2<SIQuantity,SIUnit>,Matrix2x2<?,?>>

Parameters:

mRow - the row number to retrieve (1-based)

Returns:

a row vector with the data at the given row

getColumnVector

public Vector2.Col<Q,U> getColumnVector(int col)

Description copied from class: VectorMatrix

Return a quantity column (0-based) from the vector or matrix. Note that the specific vector to return can be tightened by the implementing class.

Specified by:

getColumnVector in class VectorMatrix<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>,Matrix2x2<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>>,Matrix2x2<SIQuantity,SIUnit>,Matrix2x2<?,?>>

Parameters:

col - the column number to retrieve (0-based)

Returns:

a column vector with the data at the given column

mgetColumnVector

public Vector2.Col<Q,U> mgetColumnVector(int mCol)

Description copied from class: VectorMatrix

Return a quantity column (1-based) from the vector or matrix. Note that the specific vector to return can be tightened by the implementing class.

Specified by:

mgetColumnVector in class VectorMatrix<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>,Matrix2x2<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>>,Matrix2x2<SIQuantity,SIUnit>,Matrix2x2<?,?>>

Parameters:

mCol - the column number to retrieve (1-based)

Returns:

a column vector with the data at the given column

getDiagonalVector

public Vector2.Col<Q,U> getDiagonalVector()
                                   throws IllegalStateException

Description copied from class: SquareMatrix

Retrieve the main diagonal of the matrix as a column vector.

Specified by:

getDiagonalVector in class SquareMatrix<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>,Matrix2x2<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>>,Matrix2x2<SIQuantity,SIUnit>,Matrix2x2<?,?>>

Returns:

the main diagonal as a Vector

Throws:

IllegalStateException

inverse

public Matrix2x2<SIQuantity,SIUnit> inverse()
                                     throws NonInvertibleMatrixException

Description copied from class: SquareMatrix

Return the inverse of the square matrix, if the matrix is non-singular. The unit of the matrix is U^(-1).

Specified by:

inverse in class SquareMatrix<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>,Matrix2x2<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>>,Matrix2x2<SIQuantity,SIUnit>,Matrix2x2<?,?>>

Returns:

the inverse of the square matrix, if the matrix is non-singular

Throws:

NonInvertibleMatrixException - when the matrix is singular or cannot be inverted

adjugate

public Matrix2x2<SIQuantity,SIUnit> adjugate()

Description copied from class: SquareMatrix

Return the adjugate (classical adjoint) matrix for this matrix, often denoted as adj(M). The unit of adj(M) is U^(n-1) where n is the order of the matrix.

Specified by:

adjugate in class SquareMatrix<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>,Matrix2x2<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>>,Matrix2x2<SIQuantity,SIUnit>,Matrix2x2<?,?>>

Returns:

the adjugate (classical adjoint) matrix

invertElements

public Matrix2x2<SIQuantity,SIUnit> invertElements()

Description copied from interface: Hadamard

Invert the vector, matrix or table on an element-by-element basis.

Specified by:

invertElements in interface Hadamard<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>>

Overrides:

invertElements in class VectorMatrix<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>,Matrix2x2<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>>,Matrix2x2<SIQuantity,SIUnit>,Matrix2x2<?,?>>

Returns:

a vector, matrix or table with an element-by-element inversion (1/value) of the elements

multiplyElements

public Matrix2x2<SIQuantity,SIUnit> multiplyElements(Matrix2x2<?,?> other)

Description copied from interface: Hadamard

Multiply the elements of this vector, matrix or table on an element-by-element basis with those of another collection of the same type (but possibly representing another quantity).

Specified by:

multiplyElements in interface Hadamard<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>>

Overrides:

multiplyElements in class VectorMatrix<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>,Matrix2x2<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>>,Matrix2x2<SIQuantity,SIUnit>,Matrix2x2<?,?>>

Parameters:

other - the other collection of the same type

Returns:

a vector, matrix or table with an element-by-element multiplication of its elements

divideElements

public Matrix2x2<SIQuantity,SIUnit> divideElements(Matrix2x2<?,?> other)

Description copied from interface: Hadamard

Divide the elements of this vector, matrix or table on an element-by-element basis with those of another collection of the same type (but possibly representing another quantity).

Specified by:

divideElements in interface Hadamard<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>>

Overrides:

divideElements in class VectorMatrix<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>,Matrix2x2<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>>,Matrix2x2<SIQuantity,SIUnit>,Matrix2x2<?,?>>

Parameters:

other - the other collection of the same type

Returns:

a vector, matrix or table with an element-by-element division of this collection's elements and other's elements

multiply

public Matrix2x2<SIQuantity,SIUnit> multiply(Matrix2x2<?,?> otherMat)

Multiply this matrix with another matrix using matrix multiplication and return the result.

Parameters:

otherMat - the matrix to multiply with.

Returns:

the matrix from the multiplication with the correct unit

multiply

public Vector2.Col<SIQuantity,SIUnit> multiply(Vector2.Col<?,?> otherVec)

Multiply this matrix with a column vector, resulting in a column vector.

Parameters:

otherVec - the column vector to multiply with

Returns:

the resulting vector from the multiplication

multiplyElements

public Matrix2x2<SIQuantity,SIUnit> multiplyElements(Quantity<?,?> quantity)

Description copied from interface: Hadamard

Multiply the elements of this vector, matrix or table by the given quantity.

Specified by:

multiplyElements in interface Hadamard<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>>

Overrides:

multiplyElements in class VectorMatrix<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>,Matrix2x2<Q extends Quantity<Q,U>,U extends UnitInterface<U,Q>>,Matrix2x2<SIQuantity,SIUnit>,Matrix2x2<?,?>>

Parameters:

quantity - the scalar quantity to multiply by

Returns:

a vector, matrix or table where the elements have been multiplied by the given quantity

as

public <TQ extends Quantity<TQ,
TU>,
TU extends UnitInterface<TU,
TQ>>
Matrix2x2<TQ,TU> as(TU targetUnit)
             throws IllegalArgumentException

Return the matrix 'as' a matrix with a known quantity, using a unit to express the result in. Throw a Runtime exception when the SI units of this vector and the target vector do not match.

Type Parameters:

TQ - target quantity type

TU - target unit type

Parameters:

targetUnit - the unit to convert the matrix to

Returns:

a matrix typed in the target matrix class

Throws:

IllegalArgumentException - when the units do not match