Function diag #
Create a diagonal matrix or retrieve the diagonal of a matrix
When x is a vector, a matrix with vector x on the diagonal will be returned.
When x is a two dimensional matrix, the matrixes kth diagonal will be returned as vector.
When k is positive, the values are placed on the super diagonal.
When k is negative, the values are placed on the sub diagonal.
Syntax #
math.diag(X)
math.diag(X, format)
math.diag(X, k)
math.diag(X, k, format)
Parameters #
| Parameter | Type | Description |
|---|---|---|
x |
Matrix | Array | A two dimensional matrix or a vector |
k |
number | BigNumber | The diagonal where the vector will be filled in or retrieved. Default value: 0. |
format |
string | The matrix storage format. Default value: ‘dense’. |
Returns #
| Type | Description |
|---|---|
| Matrix | Array | Diagonal matrix from input vector, or diagonal from input matrix. |
Throws #
Type | Description —- | ———–
Examples #
// create a diagonal matrix
math.diag([1, 2, 3]) // returns [[1, 0, 0], [0, 2, 0], [0, 0, 3]]
math.diag([1, 2, 3], 1) // returns [[0, 1, 0, 0], [0, 0, 2, 0], [0, 0, 0, 3]]
math.diag([1, 2, 3], -1) // returns [[0, 0, 0], [1, 0, 0], [0, 2, 0], [0, 0, 3]]
// retrieve the diagonal from a matrix
const a = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
math.diag(a) // returns [1, 5, 9]
