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feat: add stats/base/ndarray/max-by
PR-URL: #7194 Co-authored-by: Athan Reines <[email protected]> Reviewed-by: Athan Reines <[email protected]>
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‎lib/node_modules/@stdlib/stats/base/ndarray/max-by/README.md

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<!--
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@license Apache-2.0
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Copyright (c) 2025 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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# maxBy
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> Compute the maximum value of a one-dimensional ndarray via a callback function.
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<section class="intro">
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</section>
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<!-- /.intro -->
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<section class="usage">
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## Usage
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```javascript
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var maxBy = require( '@stdlib/stats/base/ndarray/max-by' );
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```
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#### maxBy( arrays, clbk\[, thisArg ] )
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Computes the maximum value of a one-dimensional ndarray via a callback function.
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```javascript
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var ndarray = require( '@stdlib/ndarray/base/ctor' );
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function clbk( value ) {
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return value * 2.0;
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}
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var xbuf = [ 1.0, 3.0, 4.0, 2.0 ];
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var x = new ndarray( 'generic', xbuf, [ 4 ], [ 1 ], 0, 'row-major' );
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var v = maxBy( [ x ], clbk );
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// returns 8.0
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```
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The function has the following parameters:
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- **arrays**: array-like object containing a one-dimensional input ndarray.
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- **clbk**: callback function.
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- **thisArg**: callback execution context (_optional_).
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The invoked callback is provided three arguments:
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- **value**: current array element.
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- **idx**: current array element index.
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- **array**: input ndarray.
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To set the callback execution context, provide a `thisArg`.
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```javascript
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var ndarray = require( '@stdlib/ndarray/base/ctor' );
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function clbk( value ) {
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this.count += 1;
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return value * 2.0;
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}
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var xbuf = [ 1.0, 3.0, 4.0, 2.0 ];
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var x = new ndarray( 'generic', xbuf, [ 4 ], [ 1 ], 0, 'row-major' );
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var ctx = {
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'count': 0
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};
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var v = maxBy( [ x ], clbk, ctx );
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// returns 8.0
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var count = ctx.count;
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// returns 4
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```
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</section>
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<!-- /.usage -->
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<section class="notes">
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## Notes
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- If provided an empty one-dimensional ndarray, the function returns `NaN`.
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- A provided callback function should return a numeric value.
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- If a provided callback function does not return any value (or equivalently, explicitly returns `undefined`), the value is **ignored**.
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</section>
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<!-- /.notes -->
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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 discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
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var ndarray = require( '@stdlib/ndarray/base/ctor' );
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var ndarray2array = require( '@stdlib/ndarray/to-array' );
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var maxBy = require( '@stdlib/stats/base/ndarray/max-by' );
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function clbk( value ) {
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return value * 2.0;
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}
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var xbuf = discreteUniform( 10, -50, 50, {
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'dtype': 'generic'
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});
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var x = new ndarray( 'generic', xbuf, [ xbuf.length ], [ 1 ], 0, 'row-major' );
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console.log( ndarray2array( x ) );
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var v = maxBy( [ x ], clbk );
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console.log( v );
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```
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</section>
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<!-- /.examples -->
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<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->
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<section class="related">
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</section>
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<!-- /.related -->
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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 -->

‎lib/node_modules/@stdlib/stats/base/ndarray/max-by/benchmark/benchmark.js

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/**
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* @license Apache-2.0
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*
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* Copyright (c) 2025 The Stdlib Authors.
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*
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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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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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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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'use strict';
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// MODULES //
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var bench = require( '@stdlib/bench' );
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var uniform = require( '@stdlib/random/array/uniform' );
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var isnan = require( '@stdlib/math/base/assert/is-nan' );
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var pow = require( '@stdlib/math/base/special/pow' );
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var ndarray = require( '@stdlib/ndarray/base/ctor' );
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var pkg = require( './../package.json' ).name;
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var maxBy = require( './../lib' );
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// VARIABLES //
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var options = {
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'dtype': 'generic'
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};
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// FUNCTIONS //
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/**
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* Callback function.
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*
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* @private
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* @param {number} value - array element
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* @returns {number} callback result
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*/
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function clbk( value ) {
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return value * 2.0;
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}
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/**
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* Creates a benchmark function.
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*
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* @private
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* @param {PositiveInteger} len - array length
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* @returns {Function} benchmark function
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*/
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function createBenchmark( len ) {
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var xbuf;
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var x;
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xbuf = uniform( len, -10.0, 10.0, options );
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x = new ndarray( options.dtype, xbuf, [ len ], [ 1 ], 0, 'row-major' );
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return benchmark;
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function benchmark( b ) {
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var v;
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var i;
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b.tic();
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for ( i = 0; i < b.iterations; i++ ) {
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v = maxBy( [ x ], clbk );
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if ( isnan( v ) ) {
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b.fail( 'should not return NaN' );
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}
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}
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b.toc();
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if ( isnan( v ) ) {
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b.fail( 'should not return NaN' );
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}
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b.pass( 'benchmark finished' );
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b.end();
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}
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}
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// MAIN //
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/**
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* Main execution sequence.
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*
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* @private
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*/
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function main() {
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var len;
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var min;
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var max;
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var f;
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var i;
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min = 1; // 10^min
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max = 6; // 10^max
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for ( i = min; i <= max; i++ ) {
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len = pow( 10, i );
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f = createBenchmark( len );
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bench( pkg+':len='+len, f );
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}
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}
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main();

‎lib/node_modules/@stdlib/stats/base/ndarray/max-by/docs/repl.txt

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{{alias}}( arrays, clbk[, thisArg] )
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Computes the maximum value of a one-dimensional ndarray via a callback
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function.
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If provided an empty ndarray, the function returns `NaN`.
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The callback function is provided three arguments:
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- value: current array element.
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- index: current array index.
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- array: the input ndarray.
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The callback function should return a numeric value.
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If the callback function does not return any value (or equivalently,
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explicitly returns `undefined`), the value is ignored.
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Parameters
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----------
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arrays: ArrayLikeObject<ndarray>
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Array-like object containing a one-dimensional input ndarray.
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clbk: Function
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Callback function.
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thisArg: any (optional)
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Callback execution context.
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Returns
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-------
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out: number
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Maximum value.
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Examples
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--------
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> var xbuf = [ 1.0, -2.0, 2.0 ];
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> var dt = 'generic';
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> var sh = [ xbuf.length ];
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> var sx = [ 1 ];
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> var ox = 0;
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> var ord = 'row-major';
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> var x = new {{alias:@stdlib/ndarray/ctor}}( dt, xbuf, sh, sx, ox, ord );
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> function f ( v ) { return v * 2.0; };
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> {{alias}}( [ x ], f )
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4.0
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See Also
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--------
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