187 lines
4.4 KiB
Markdown
187 lines
4.4 KiB
Markdown
<!--
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@license Apache-2.0
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Copyright (c) 2018 The Stdlib Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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# ind2sub
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> Convert a linear index to an array of subscripts.
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<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->
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<section class="intro">
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</section>
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<!-- /.intro -->
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<!-- Package usage documentation. -->
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<section class="usage">
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## Usage
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```javascript
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var ind2sub = require( '@stdlib/ndarray/ind2sub' );
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```
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#### ind2sub( shape, idx\[, options] )
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Converts a linear index to an array of subscripts.
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```javascript
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var shape = [ 2, 2 ];
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var s = ind2sub( shape, 2 );
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// returns [ 1, 0 ]
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```
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The function supports the following `options`:
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- `mode`: specifies how to handle a linear index which exceeds array dimensions. The following modes are supported:
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- `throw`: specifies that the function should throw an error when a linear index exceeds array dimensions.
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- `wrap`: specifies that the function should wrap around a linear index exceeding array dimensions using modulo arithmetic.
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- `clamp`: specifies that the function should set a linear index exceeding array dimensions to either `0` (minimum linear index) or the maximum linear index.
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- `order`: specifies whether an array is `row-major` (C-style) or `column-major` (Fortran-style). Default: `'row-major'`.
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By default, the function assumes a row-major array. To return subscripts for a column-major array, set the `order` option.
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```javascript
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var shape = [ 2, 2 ];
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var opts = {};
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opts.order = 'column-major';
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var s = ind2sub( shape, 1, opts );
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// returns [ 1, 0 ]
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```
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By default, the function throws an `error` if provided a linear index which exceeds array dimensions. To specify alternative behavior, set the `mode` option.
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```javascript
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var shape = [ 2, 2 ];
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var opts = {};
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opts.mode = 'wrap';
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var s = ind2sub( shape, -5, opts );
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// returns [ 1, 1 ]
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opts.mode = 'clamp';
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s = ind2sub( shape, 7, opts );
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// returns [ 1, 1 ]
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```
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#### ind2sub.assign( shape, idx\[, options], out )
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Converts a linear index to an array of subscripts and assigns results to a provided output array.
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```javascript
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var shape = [ 2, 2 ];
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var out = [ 0, 0 ];
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var subscripts = ind2sub.assign( shape, 1, out );
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// returns [ 0, 1 ]
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var bool = ( subscripts === out );
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// returns true
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```
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The function accepts the same `options` as above.
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</section>
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<!-- /.usage -->
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<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="notes">
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</section>
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<!-- /.notes -->
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<!-- Package usage examples. -->
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<section class="examples">
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## Examples
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<!-- eslint no-undef: "error" -->
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```javascript
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var numel = require( '@stdlib/ndarray/base/numel' );
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var ind2sub = require( '@stdlib/ndarray/ind2sub' );
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var shape = [ 3, 3, 3 ];
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var len = numel( shape );
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var arr = [];
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var i;
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for ( i = 0; i < len; i++ ) {
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arr.push( i );
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}
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var opts = {
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'order': 'column-major'
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};
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console.log( '' );
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console.log( 'Dimensions: %s.', shape.join( 'x' ) );
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console.log( 'View (subscripts):' );
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console.log( '' );
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var row;
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var s;
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row = ' ';
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for ( i = 0; i < len; i++ ) {
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s = ind2sub( shape, i, opts );
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row += '(' + s.join( ',' ) + ')';
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if ( (i+1)%shape[0] === 0 ) {
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console.log( row );
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row = ' ';
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} else {
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row += ', ';
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}
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if ( (i+1)%(shape[0]*shape[1]) === 0 ) {
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console.log( '' );
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}
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}
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```
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</section>
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<!-- /.examples -->
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<!-- 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. -->
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<section class="references">
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</section>
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<!-- /.references -->
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<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="links">
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</section>
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<!-- /.links -->
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