62 lines
1.6 KiB
Markdown
62 lines
1.6 KiB
Markdown
|
<!-- Note: This file is automatically generated from source code comments. Changes made in this file will be overridden. -->
|
||
|
|
|
||
|
|
# 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 `k`th 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
|
||
|
|
|
||
|
|
```js
|
||
|
|
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
|
||
|
|
|
||
|
|
```js
|
||
|
|
// 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]
|
||
|
|
```
|
||
|
|
|
||
|
|
|
||
|
|
## See also
|
||
|
|
|
||
|
|
[ones](ones.md),
|
||
|
|
[zeros](zeros.md),
|
||
|
|
[identity](identity.md)
|