This can be done by creating a boolean array that represents the desired conditions, and then using that array as an index to select the elements of the original array that meet those conditions.įor example, a boolean array can be created to represent all the even numbers in an array, and then used to filter the original array to only include the even numbers. Advanced Indexing #īoolean array indexing is a technique that allows you to filter, replace, and set values in an array based on logical conditions. The optional third argument defaultValue. Initialized with zero, but it is possible to specify an alternative value using When setting a value at a location outside of the current matrix size using the It is important to note that the set method willĬonst p = math. There are two methods available on matrices that allow to get or set a single index ( 1, 2 ), 5 ) // Matrix,, ] Getting and setting a value in a matrix # The subset will be applied to the matrix itself c. index ( 2, ), ) // Array,, , ] // replace a subset. The subset will be applied to a clone of the matrix math. index ( 1, 2 )) // 5 // replace a subset. index (, 0 )) // Matrix,, ] // get a subset d. create some matrices const a = const b =, ] const c = math. Note that mathematical applications like MatlabĪnd Octave work differently, as they use one-based indexes. Matrix indexes in math.js are zero-based, like most programming languages Single value in a matrix, the value itself is returned. The function subset normally returns a subset, but when getting or setting a Subset will return the value itself instead of a matrix containing just this When getting a single value from a matrix, An Index can beĬreated using the function index. Or a set of values for each dimension of a matrix. In the matrix, and if not, a subset of the matrix will be returned.Ī subset can be defined using an Index. When parameter replacement is provided, the function will replace a subset The static function subset(matrix, index ) can be used. Matrices have a subset function, which is applied to the matrix itself: Subsets of a matrix can be retrieved or replaced using the function subset. index ( 1, 0 )) // 2 and not ] Getting or replacing subsets # squeeze (]) // 3 // when getting/setting a single value in a matrix using subset, // it automatically squeeze/unsqueeze the value const b = math. Normally rendered as the column, and the second dimension is rendered as When creating and printing a two dimensional matrix, the first dimension is Note that the dimensions themselves do not have a meaning attached. size () // Array, // get the size of a multi-dimensional matrix const c =, ],, ]] math. size ( b ) // Matrix, // matrices have a function size (always returns an Array) b. size ( ' hello world ' ) // Matrix, // get the size of a two-dimensional matrix const a = ] // Array const b = math. unit ( ' 5.3 mm ' )) // Matrix, // get the size of a one-dimensional matrix (a vector) and a string math. Note that in case of numbers as arguments, the output isĭetermined by the option matrix as discussed in section When the input is a Matrix, the output willīe a Matrix. Or matrix containing the dimensions for the matrix. The functions ones, zeros, and identity also accept a single array identity ( 3 ) // Matrix, size, ,, ] math. ones ( 2, 2 ), 5 ) // Matrix, size, , ] // identity creates an identity matrix math. zeros ( 2, 2, 2 ) // Matrix, size, //, ],, ]] // ones creates a matrix filled with ones math. zeros ( 3, 2 ) // Matrix, size, ,, ] math. zeros creates a matrix filled with zeros math. Which can be a string 'Matrix' (default) or 'Array'. Input, the output is determined by the configuration option matrix, In case of mixed input, a Matrix is returned.įor functions where the type of output cannot be determined from the In most cases, the type of matrix output from functions is determined by theįunction input: An Array as input will return an Array, a Matrix as input Matrix manipulation such as subset, size, resize, clone, and more. A Matrix is an object wrappedĪround a regular JavaScript Array, providing utility functions for easy Matrix, a matrix implementation by math.js.math.js supports bothĭense and sparse matrices. Interchangeably in all relevant math.js functions. Both regular JavaScriptĪrrays as well as the matrix type implemented by math.js can be used Matrices can beĬreated, manipulated, and used in calculations. Math.js supports multi dimensional matrices and arrays.
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