Matrix

Stand-alone Linear Algebra Library for PHP

Installation

composer require mcordingley/LinearAlgebra

Alternately, include this in your composer.json and then update:

"mcordingley/linearalgebra": "^1.3.0"

If Composer isn't an option for you, clone this repository and run build-phar.php to generate a phar archive that you can include into your project. PHP will autoload classes from inside the archive as needed.

Usage

Start with a use statement for the class:

use mcordingley\LinearAlgebra\Matrix;

Then, instantiate a new instance of the matrix class like so:

$matrix = new Matrix([
    [0, 1, 2],
    [3, 4, 5],
    [6, 7, 8]
]);

You can also generate an identity matrix with the identity factory function:

$threeByThreeIdentityMatrix = Matrix::identity(3);

With the matrix instance, you can retrieve individual elements with get using the zero-based indices of the row and column that you want:

$element = $matrix->get($row, $column);

It's also possible to find out how large the matrix is with getRowCount() and getColumnCount():

$rows = $matrix->getRowCount();
$columns = $matrix->getColumnCount();

You can also add, subtract, and multiply the matrix with scalar values and other matrices. All operations return a new Matrix and do not modify the underlying matrix:

$addedScalar = $matrix->addScalar(3);
$addedMatrix = $matrix->addMatrix($anotherMatrix);
$subtractedScalar = $matrix->subtractScalar(2);
$subtractedMatrix = $matrix->subtractMatrix($anotherMatrix);
$multipliedByScalar = $matrix->multiplyScalar(4);
$multipliedByMatrix = $matrix->multiplyMatrix($anotherMatrix);

Matrices can be compared with equals to see if they're equal:

if ($matrix1->equals($matrix2)) {
    // Equality for all!
}

In addition to these basic operations, the Matrix class offers other common matrix operations:

$matrix->inverse()
$matrix->adjoint()
$matrix->determinant()
$matrix->trace()
$matrix->transpose()
$matrix->submatrix()

It's also possible to run a map over the matrix:

$squaredElements = $matrix->map(function($element, $row, $column, $matrix) {
    return $element * $element
});

If you need to combine together matrices, you can do so by calling the concatenation methods:

$m1 = new Matrix([
  [1,2,3],
  [4,5,6],
]);

$m2 = new Matrix([
  [7],
  [8],
]);

$m3 = new Matrix([[3,2,1]]);

$m4 = $m1->concatenateRight($m2);
//  [
//      [1,2,3,7],
//      [4,5,6,8],
//  ]

$m5 = $m1->concatenateBottom($m3);
// [
//     [1,2,3],
//     [4,5,6],
//     [3,2,1],
// ]

Change-log

• 2.0.0 (future)

  • Drop support for PHP 5.x
  • Introduce strict scalar type hints
  • Drop deprecated functions and properties.
  • Tighten up interface with the final and private keywords.

• 1.4.0 (future)

  • Add entrywise() to compute the Hadamard product.

• 1.3.2

  • Deprecate __toString() magic method.
  • Deprecate isSymmetric().

• 1.3.1

  • Deprecate use of the ArrayAccess interface.
  • More internal code style fixes.

• 1.3.0

  • Fix typo in names of concatenateRight() and concatenateBottom()
  • Remove generated Phar file. Users who need it should use the build-phar.php script to generate one.
  • Refactor LUDecomposition to have a less awkward constructor.
  • Split add() into addMatrix() and addScalar(). Deprecate add().
  • Split subtract() into subtractMatrix() and subtractScalar(). Deprecate subtract().
  • Split multiply() into multiplyMatrix() and multiplyScalar(). Deprecate multiply().
  • Add getRowCount() and getColumnCount() accessors.
  • Deprecate rows and columns properties.

• 1.2.0

  • Added concatenateBottom($other)
  • Added concatencateRight($other)

• 1.1.0

  • Added diagonal().

• 1.0.0

  • Switch to PSR-4 from PSR-0.
  • Take isSymmetric() public.
  • Rearrange source in Matrix.php to be more readable and PSR-compliant.

• 0.9.1

  • Fix several bugs with the Cholesky decomposition and inverse.

• 0.9.0

  • Bump version up to represent that this is close to it's final form.
  • Merged PR for faster inverse calculations
  • KISS Vector class good-bye.
  • Renamed eq to equals.
  • Removed set function, so instantiated objects are immutable.

• 0.3.0

  • Added the identity factory function
  • Using Cholesky decomposition for faster matrix inversions for applicable matrices
  • Added eq function to test equality of matrices
  • Implemented the ArrayAccess interface

• 0.2.0

  • Created the Vector type
  • \MCordingley namespace is now \mcordingley
  • Matrix functions that return a new Matrix now return a new instance of the called class

• 0.1.0

  • Created the Matrix type
  • Scalar Addition
  • Scalar Subtraction
  • Scalar Multiplication
  • Matrix Addition
  • Matrix Subtraction
  • Matrix Multiplication
  • Inverse
  • Adjoint
  • Determinant
  • Trace
  • Transpose
  • Submatrix
  • Map