Package Exports

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

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Readme

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maxBy

Compute the maximum value of a one-dimensional ndarray via a callback function.

Installation

npm install @stdlib/stats-base-ndarray-max-by

Usage

var maxBy = require( '@stdlib/stats-base-ndarray-max-by' );

maxBy( arrays, clbk[, thisArg ] )

Computes the maximum value of a one-dimensional ndarray via a callback function.

var ndarray = require( '@stdlib/ndarray-base-ctor' );

function clbk( value ) {
    return value * 2.0;
}

var xbuf = [ 1.0, 3.0, 4.0, 2.0 ];
var x = new ndarray( 'generic', xbuf, [ 4 ], [ 1 ], 0, 'row-major' );

var v = maxBy( [ x ], clbk );
// returns 8.0

The function has the following parameters:

arrays: array-like object containing a one-dimensional input ndarray.
clbk: callback function.
thisArg: callback execution context (optional).

The invoked callback is provided three arguments:

value: current array element.
idx: current array element index.
array: input ndarray.

To set the callback execution context, provide a thisArg.

var ndarray = require( '@stdlib/ndarray-base-ctor' );

function clbk( value ) {
    this.count += 1;
    return value * 2.0;
}

var xbuf = [ 1.0, 3.0, 4.0, 2.0 ];
var x = new ndarray( 'generic', xbuf, [ 4 ], [ 1 ], 0, 'row-major' );
var ctx = {
    'count': 0
};

var v = maxBy( [ x ], clbk, ctx );
// returns 8.0

var count = ctx.count;
// returns 4

Notes

If provided an empty one-dimensional ndarray, the function returns NaN.
A provided callback function should return a numeric value.
If a provided callback function does not return any value (or equivalently, explicitly returns undefined), the value is ignored.

Examples

var discreteUniform = require( '@stdlib/random-array-discrete-uniform' );
var ndarray = require( '@stdlib/ndarray-base-ctor' );
var ndarray2array = require( '@stdlib/ndarray-to-array' );
var maxBy = require( '@stdlib/stats-base-ndarray-max-by' );

function clbk( value ) {
    return value * 2.0;
}

var xbuf = discreteUniform( 10, -50, 50, {
    'dtype': 'generic'
});
var x = new ndarray( 'generic', xbuf, [ xbuf.length ], [ 1 ], 0, 'row-major' );
console.log( ndarray2array( x ) );

var v = maxBy( [ x ], clbk );
console.log( v );

Notice

This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

Community

License

See LICENSE.

@stdlib/stats-base-ndarray-max-by