simple-squiggle/node_modules/mathjs/docs/reference/functions/subset.md

Function subset

Get or set a subset of a matrix or string.

Syntax

math.subset(value, index)                                // retrieve a subset
math.subset(value, index, replacement [, defaultValue])  // replace a subset

Parameters

Parameter	Type	Description
matrix	Array | Matrix | string	An array, matrix, or string
index	Index	For each dimension of the target, specifies an index or a list of indices to fetch or set. subset uses the cartesian product of the indices specified in each dimension.
replacement	*	An array, matrix, or scalar. If provided, the subset is replaced with replacement. If not provided, the subset is returned
defaultValue	*	Default value, filled in on new entries when the matrix is resized. If not provided, math.matrix elements will be left undefined. Default value: undefined.

Returns

Type	Description
Array | Matrix | string	Either the retrieved subset or the updated matrix.

Throws

Type	Description

Examples

// get a subset
const d = [[1, 2], [3, 4]]
math.subset(d, math.index(1, 0))        // returns 3
math.subset(d, math.index([0, 1], 1))   // returns [[2], [4]]

// replace a subset
const e = []
const f = math.subset(e, math.index(0, [0, 2]), [5, 6])  // f = [[5, 6]] and e = [[5, 0, 6]]
const g = math.subset(f, math.index(1, 1), 7, 0)         // g = [[5, 6], [0, 7]]

// get submatrix using ranges
const M = [
  [1,2,3],
  [4,5,6],
  [7,8,9]
]
math.subset(M, math.index(math.range(0,2), math.range(0,3))) // [[1,2,3],[4,5,6]]

See also

size, resize, squeeze, index