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 #
| Parameter |
Type |
Description |
size |
Array | Matrix |
The size of the matrix to be created |
fn |
function |
Callback function invoked for every entry in the matrix |
format |
string |
The Matrix storage format, either 'dense' or 'sparse' |
datatype |
string |
Type of the values |
Returns #
| Type |
Description |
| Array | Matrix |
Returns the created matrix |
Throws #
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
