66 lines
1.8 KiB
Markdown
66 lines
1.8 KiB
Markdown
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<!-- Note: This file is automatically generated from source code comments. Changes made in this file will be overridden. -->
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# Function subset
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Get or set a subset of a matrix or string.
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## Syntax
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```js
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math.subset(value, index) // retrieve a subset
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math.subset(value, index, replacement [, defaultValue]) // replace a subset
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```
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### Parameters
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Parameter | Type | Description
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--------- | ---- | -----------
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`matrix` | Array | Matrix | string | An array, matrix, or string
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`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.
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`replacement` | * | An array, matrix, or scalar. If provided, the subset is replaced with replacement. If not provided, the subset is returned
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`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.
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### Returns
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Type | Description
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---- | -----------
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Array | Matrix | string | Either the retrieved subset or the updated matrix.
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### Throws
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Type | Description
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---- | -----------
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## Examples
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```js
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// get a subset
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const d = [[1, 2], [3, 4]]
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math.subset(d, math.index(1, 0)) // returns 3
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math.subset(d, math.index([0, 1], 1)) // returns [[2], [4]]
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// replace a subset
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const e = []
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const f = math.subset(e, math.index(0, [0, 2]), [5, 6]) // f = [[5, 6]] and e = [[5, 0, 6]]
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const g = math.subset(f, math.index(1, 1), 7, 0) // g = [[5, 6], [0, 7]]
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// get submatrix using ranges
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const M = [
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[1,2,3],
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[4,5,6],
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[7,8,9]
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]
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math.subset(M, math.index(math.range(0,2), math.range(0,3))) // [[1,2,3],[4,5,6]]
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```
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## See also
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[size](size.md),
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[resize](resize.md),
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[squeeze](squeeze.md),
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[index](index.md)
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