Function matrixFromFunction #

Create a matrix by evaluating a generating function at each index. The simplest overload returns a multi-dimensional array as long as size is an array. Passing size as a Matrix or specifying a format will result in returning a Matrix.

Syntax #

math.matrixFromFunction(size, fn)
math.matrixFromFunction(size, fn, format)
math.matrixFromFunction(size, fn, format, datatype)
math.matrixFromFunction(size, format, fn)
math.matrixFromFunction(size, format, datatype, fn)

Where #

• size: (number[] | Matrix) A vector giving the extent of the array to be created in each dimension. If size has one entry, a vector is created; if it has two, a rectangular array/Matrix is created; if three, a three-dimensional array/Matrix is created; and so on.
• fn: (index: number[]) => MathType The callback function that will generate the entries of the matrix. It is called in turn with the index of each entry of the matrix. The index is always an ordinary array of numbers with the same length as size. So for vectors, you will get indices like [0] or [1], whereas for matrices, you will get indices like [2, 0] or [1,3]. The return value may be any type that can go in an array or Matrix entry, although if you supply the datatype argument, you must yourself ensure the type of the return value matches. Note that currently, your callback fn will receive 0-based indices for the matrix entries, regardless of whether matrixFromFunction is invoked directly from JavaScript or via the mathjs expression language.
• format: 'dense'|'sparse' Specifies the storage format for the resulting Matrix. Note that if this argument is given, the return value will always be a Matrix (rather than possibly an Array).
• datatype: string Specifies the data type of entries of the new matrix. If given, it should be the name of a data type that mathjs supports, as returned by the math.typeOf function. It is up to the caller to make certain that all values returned by fn are consistent with this datatype if specified.

Parameters #

Returns #

Throws #

Type | Description —- | ———–

Examples #

math.matrixFromFunction([3,3], i => i[0] - i[1]) // an antisymmetric matrix
math.matrixFromFunction([100, 100], 'sparse', i => i[0] - i[1] === 1 ? 4 : 0) // a sparse subdiagonal matrix
math.matrixFromFunction([5], i => math.random()) // a random vector

See also #

matrix, typeOf, zeros