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@stdlib/utils-map-reduce-right
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We believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we've built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js.
The library is fully decomposable, being architected in such a way that you can swap out and mix and match APIs and functionality to cater to your exact preferences and use cases.
When you use stdlib, you can be absolutely certain that you are using the most thorough, rigorous, well-written, studied, documented, tested, measured, and high-quality code out there.
To join us in bringing numerical computing to the web, get started by checking us out on GitHub, and please consider financially supporting stdlib. We greatly appreciate your continued support!
Perform a single-pass map-reduce operation against each element in an array while iterating from right to left and return the accumulated result.
npm install @stdlib/utils-map-reduce-right
var mapReduceRight = require( '@stdlib/utils-map-reduce-right' );
Performs a map-reduce operation against each element in an array while iterating from right to left and returns the accumulated result.
function square( value ) {
return value * value;
}
function sum( accumulator, value ) {
return accumulator + value;
}
var arr = [ 1, 2, 3, 4 ];
var out = mapReduceRight( arr, 0, square, sum );
// returns 30
The function accepts both array-like objects and ndarray
-like objects.
var array = require( '@stdlib/ndarray-array' );
function square( value ) {
return value * value;
}
function sum( accumulator, value ) {
return accumulator + value;
}
var opts = {
'dtype': 'generic'
};
var arr = array( [ [ 1, 2, 3 ], [ 4, 5, 6 ] ], opts );
var out = mapReduceRight( arr, 0, square, sum );
// returns 91
The mapping function is provided the following arguments:
The reducing function is provided the following arguments:
To set the this
context when invoking the reducing function, provide a thisArg
.
function square( value ) {
return value * value;
}
function sum( accumulator, value ) {
this.count += 1;
return accumulator + value;
}
var arr = [ 1, 2, 3, 4 ];
var ctx = {
'count': 0
};
var out = mapReduceRight( arr, 0, square, sum, ctx );
// returns 30
var mean = out / ctx.count;
// returns 7.5
The function supports array-like objects exposing getters and setters for array element access (e.g., Complex64Array
, Complex128Array
, etc).
var Complex64Array = require( '@stdlib/array-complex64' );
var Complex64 = require( '@stdlib/complex-float32' );
var cceil = require( '@stdlib/math-base-special-cceil' );
var realf = require( '@stdlib/complex-realf' );
var imagf = require( '@stdlib/complex-imagf' );
function sum( acc, z ) {
var re1 = realf( acc );
var im1 = imagf( acc );
var re2 = realf( z );
var im2 = imagf( z );
return new Complex64( re1+re2, im1+im2 );
}
var x = new Complex64Array( [ 1.5, 2.5, 3.5, 4.5, 5.5, 6.5, 7.5, 8.5 ] );
var v = mapReduceRight( x, new Complex64( 0.0, 0.0 ), cceil, sum );
// returns <Complex64>
var re = realf( v );
// returns 20.0
var im = imagf( v );
// returns 24.0
For ndarray
-like objects, the function performs a single-pass map-reduce operation over the entire input ndarray
(i.e., higher-order ndarray
dimensions are flattened to a single-dimension).
When applying a function to ndarray
-like objects, performance will be best for ndarray
-like objects which are single-segment contiguous.
var filledarrayBy = require( '@stdlib/array-filled-by' );
var discreteUniform = require( '@stdlib/random-base-discrete-uniform' ).factory;
var naryFunction = require( '@stdlib/utils-nary-function' );
var add = require( '@stdlib/math-base-ops-add' );
var abs = require( '@stdlib/math-base-special-abs' );
var array = require( '@stdlib/ndarray-array' );
var mapReduceRight = require( '@stdlib/utils-map-reduce-right' );
function fill( i ) {
var rand = discreteUniform( -10*(i+1), 10*(i+1) );
return filledarrayBy( 10, 'generic', rand );
}
// Create a two-dimensional ndarray (i.e., a matrix):
var x = array( filledarrayBy( 10, 'generic', fill ), {
'dtype': 'generic',
'flatten': true
});
// Create an explicit unary function:
var f1 = naryFunction( abs, 1 );
// Create an explicit binary function:
var f2 = naryFunction( add, 2 );
// Compute the sum of absolute values:
var out = mapReduceRight( x, 0, f1, f2 );
console.log( 'x:' );
console.log( x.data );
console.log( 'sum: %d', out );
@stdlib/utils-map-right
: apply a function to each element in an array and assign the result to an element in an output array, iterating from right to left.@stdlib/utils-map-reduce
: perform a single-pass map-reduce operation against each element in an array and return the accumulated result.@stdlib/utils-reduce-right
: apply a function against an accumulator and each element in an array while iterating from right to left and return the accumulated result.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.
See LICENSE.
Copyright © 2016-2024. The Stdlib Authors.
FAQs
Perform a single-pass map-reduce operation against each element in an array while iterating from right to left and return the accumulated result.
The npm package @stdlib/utils-map-reduce-right receives a total of 13 weekly downloads. As such, @stdlib/utils-map-reduce-right popularity was classified as not popular.
We found that @stdlib/utils-map-reduce-right demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 4 open source maintainers collaborating on the project.
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