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| 1 | +<!-- |
| 2 | +
|
| 3 | +@license Apache-2.0 |
| 4 | +
|
| 5 | +Copyright (c) 2026 The Stdlib Authors. |
| 6 | +
|
| 7 | +Licensed under the Apache License, Version 2.0 (the "License"); |
| 8 | +you may not use this file except in compliance with the License. |
| 9 | +You may obtain a copy of the License at |
| 10 | +
|
| 11 | + http://www.apache.org/licenses/LICENSE-2.0 |
| 12 | +
|
| 13 | +Unless required by applicable law or agreed to in writing, software |
| 14 | +distributed under the License is distributed on an "AS IS" BASIS, |
| 15 | +WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 16 | +See the License for the specific language governing permissions and |
| 17 | +limitations under the License. |
| 18 | +
|
| 19 | +--> |
| 20 | + |
| 21 | +# rotr90 |
| 22 | + |
| 23 | +> Rotate a matrix (or a stack of matrices) 90 degrees clockwise. |
| 24 | +
|
| 25 | +<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. --> |
| 26 | + |
| 27 | +<section class="intro"> |
| 28 | + |
| 29 | +</section> |
| 30 | + |
| 31 | +<!-- /.intro --> |
| 32 | + |
| 33 | +<!-- Package usage documentation. --> |
| 34 | + |
| 35 | +<section class="usage"> |
| 36 | + |
| 37 | +## Usage |
| 38 | + |
| 39 | +```javascript |
| 40 | +var rotr90 = require( '@stdlib/ndarray/base/rotr90' ); |
| 41 | +``` |
| 42 | + |
| 43 | +#### rotr90( x, k, writable ) |
| 44 | + |
| 45 | +Rotates a matrix (or a stack of matrices) 90 degrees clockwise. |
| 46 | + |
| 47 | +```javascript |
| 48 | +var array = require( '@stdlib/ndarray/array' ); |
| 49 | + |
| 50 | +var x = array( [ [ 1, 2 ], [ 3, 4 ] ] ); |
| 51 | +// returns <ndarray>[ [ 1, 2 ], [ 3, 4 ] ] |
| 52 | + |
| 53 | +var y = rotr90( x, 1, false ); |
| 54 | +// returns <ndarray>[ [ 3, 1 ], [ 4, 2 ] ] |
| 55 | +``` |
| 56 | + |
| 57 | +The function accepts the following arguments: |
| 58 | + |
| 59 | +- **x**: input ndarray. |
| 60 | +- **k**: number of times to rotate by 90 degrees. Positive values rotate clockwise. Negative values rotate counterclockwise. |
| 61 | +- **writable**: boolean indicating whether a returned ndarray should be writable. |
| 62 | + |
| 63 | +</section> |
| 64 | + |
| 65 | +<!-- /.usage --> |
| 66 | + |
| 67 | +<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. --> |
| 68 | + |
| 69 | +<section class="notes"> |
| 70 | + |
| 71 | +## Notes |
| 72 | + |
| 73 | +- The `writable` parameter **only** applies to ndarray constructors supporting **read-only** instances. |
| 74 | +- If `k > 0`, the function rotates the matrix clockwise. |
| 75 | +- If `k < 0`, the function rotates the matrix counterclockwise. |
| 76 | +- The returned ndarray is a **view** of the input ndarray. Accordingly, writing to the original ndarray will **mutate** the returned ndarray and vice versa. |
| 77 | +- If provided an ndarray with fewer than two dimensions, the function does not perform rotation and simply returns a new view of the input ndarray. |
| 78 | + |
| 79 | +</section> |
| 80 | + |
| 81 | +<!-- /.notes --> |
| 82 | + |
| 83 | +<!-- Package usage examples. --> |
| 84 | + |
| 85 | +<section class="examples"> |
| 86 | + |
| 87 | +## Examples |
| 88 | + |
| 89 | +<!-- eslint no-undef: "error" --> |
| 90 | + |
| 91 | +```javascript |
| 92 | +var array = require( '@stdlib/ndarray/array' ); |
| 93 | +var ndarray2array = require( '@stdlib/ndarray/to-array' ); |
| 94 | +var rotr90 = require( '@stdlib/ndarray/base/rotr90' ); |
| 95 | + |
| 96 | +// Create a 2x3 matrix: |
| 97 | +var x = array( [ [ 1, 2, 3 ], [ 4, 5, 6 ] ] ); |
| 98 | + |
| 99 | +// Rotate 90 degrees clockwise: |
| 100 | +var y = rotr90( x, 1, false ); |
| 101 | +var arr = ndarray2array( y ); |
| 102 | +// returns [ [ 4, 1 ], [ 5, 2 ], [ 6, 3 ] ] |
| 103 | + |
| 104 | +// Rotate 180 degrees: |
| 105 | +y = rotr90( x, 2, false ); |
| 106 | +arr = ndarray2array( y ); |
| 107 | +// returns [ [ 6, 5, 4 ], [ 3, 2, 1 ] ] |
| 108 | + |
| 109 | +// Rotate 270 degrees clockwise (equivalent to 90 degrees counterclockwise): |
| 110 | +y = rotr90( x, 3, false ); |
| 111 | +arr = ndarray2array( y ); |
| 112 | +// returns [ [ 3, 6 ], [ 2, 5 ], [ 1, 4 ] ] |
| 113 | + |
| 114 | +// Rotate 360 degrees (equivalent to no rotation): |
| 115 | +y = rotr90( x, 4, false ); |
| 116 | +arr = ndarray2array( y ); |
| 117 | +// returns [ [ 1, 2, 3 ], [ 4, 5, 6 ] ] |
| 118 | + |
| 119 | +// Rotate 90 degrees counterclockwise (equivalent to 270 degrees clockwise): |
| 120 | +y = rotr90( x, -1, false ); |
| 121 | +arr = ndarray2array( y ); |
| 122 | +// returns [ [ 3, 6 ], [ 2, 5 ], [ 1, 4 ] ] |
| 123 | +``` |
| 124 | + |
| 125 | +</section> |
| 126 | + |
| 127 | +<!-- /.examples --> |
| 128 | + |
| 129 | +<!-- Section to include cited references. If references are included, add a horizontal rule *before* the section. Make sure to keep an empty line after the `section` element and another before the `/section` close. --> |
| 130 | + |
| 131 | +<section class="references"> |
| 132 | + |
| 133 | +</section> |
| 134 | + |
| 135 | +<!-- /.references --> |
| 136 | + |
| 137 | +<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. --> |
| 138 | + |
| 139 | +<section class="related"> |
| 140 | + |
| 141 | +</section> |
| 142 | + |
| 143 | +<!-- /.related --> |
| 144 | + |
| 145 | +<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. --> |
| 146 | + |
| 147 | +<section class="links"> |
| 148 | + |
| 149 | +<!-- <related-links> --> |
| 150 | + |
| 151 | +<!-- </related-links> --> |
| 152 | + |
| 153 | +</section> |
| 154 | + |
| 155 | +<!-- /.links --> |
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