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Apply a function to each element in an array and assign the result to an element in an output array.
import map from 'https://cdn.jsdelivr.net/gh/stdlib-js/utils-map@deno/mod.js';You can also import the following named exports from the package:
import { assign } from 'https://cdn.jsdelivr.net/gh/stdlib-js/utils-map@deno/mod.js';Applies a function to each element in an array and assigns the result to an element in a new array.
import naryFunction from 'https://cdn.jsdelivr.net/gh/stdlib-js/utils-nary-function@deno/mod.js';
import abs from 'https://cdn.jsdelivr.net/gh/stdlib-js/math-base-special-abs@deno/mod.js';
var arr = [ -1, -2, -3, -4, -5, -6 ];
var out = map( arr, naryFunction( abs, 1 ) );
// returns [ 1, 2, 3, 4, 5, 6 ]The function accepts both array-like objects and ndarray-like objects.
import naryFunction from 'https://cdn.jsdelivr.net/gh/stdlib-js/utils-nary-function@deno/mod.js';
import abs from 'https://cdn.jsdelivr.net/gh/stdlib-js/math-base-special-abs@deno/mod.js';
import array from 'https://cdn.jsdelivr.net/gh/stdlib-js/ndarray-array@deno/mod.js';
var opts = {
'dtype': 'generic'
};
var arr = array( [ [ -1, -2, -3 ], [ -4, -5, -6 ] ], opts );
var out = map( arr, naryFunction( abs, 1 ) );
// returns <ndarray>
var v = out.get( 1, 1 );
// returns 5The applied function is provided the following arguments:
- value: array element.
- index: element index.
- arr: input array.
To set the this context when invoking the input function, provide a thisArg.
import abs from 'https://cdn.jsdelivr.net/gh/stdlib-js/math-base-special-abs@deno/mod.js';
function fcn( v ) {
this.count += 1;
return abs( v );
}
var arr = [ -1, -2, -3, -4, -5, -6 ];
var ctx = {
'count': 0
};
var out = map( arr, fcn, ctx );
// returns [ 1, 2, 3, 4, 5, 6 ]
var cnt = ctx.count;
// returns 6Applies a function to each element in an array and assigns the result to an element in an output array.
import naryFunction from 'https://cdn.jsdelivr.net/gh/stdlib-js/utils-nary-function@deno/mod.js';
import abs from 'https://cdn.jsdelivr.net/gh/stdlib-js/math-base-special-abs@deno/mod.js';
var arr = [ -1, -2, -3, -4, -5, -6 ];
var out = [ 0, 0, 0, 0, 0, 0 ];
map.assign( arr, out, naryFunction( abs, 1 ) );
console.log( out );
// => [ 1, 2, 3, 4, 5, 6 ]The method accepts both array-like objects and ndarray-like objects.
import naryFunction from 'https://cdn.jsdelivr.net/gh/stdlib-js/utils-nary-function@deno/mod.js';
import abs from 'https://cdn.jsdelivr.net/gh/stdlib-js/math-base-special-abs@deno/mod.js';
import array from 'https://cdn.jsdelivr.net/gh/stdlib-js/ndarray-array@deno/mod.js';
var opts = {
'dtype': 'generic',
'shape': [ 2, 3 ]
};
var arr = array( [ [ -1, -2, -3 ], [ -4, -5, -6 ] ], opts );
var out = array( opts );
map.assign( arr, out, naryFunction( abs, 1 ) );
var v = out.get( 1, 1 );
// returns 5Input and output arrays must be either both array-like objects or both ndarray-like objects. If input and output arrays are both array-like objects, both arrays must have the same number of elements.
If input and output arrays are both ndarray-like objects, the arrays must be broadcast compatible. To map from an input ndarray to an output ndarray which has the same rank (i.e., dimensionality) and the same number of elements, but which is not broadcast compatible, reshape the arrays prior to invocation.
import naryFunction from 'https://cdn.jsdelivr.net/gh/stdlib-js/utils-nary-function@deno/mod.js';
import abs from 'https://cdn.jsdelivr.net/gh/stdlib-js/math-base-special-abs@deno/mod.js';
import array from 'https://cdn.jsdelivr.net/gh/stdlib-js/ndarray-array@deno/mod.js';
var opts = {
'dtype': 'generic',
'shape': [ 2, 3 ]
};
var arr = array( [ [ -1, -2, -3 ], [ -4, -5, -6 ] ], opts );
opts = {
'dtype': 'generic',
'shape': [ 2, 2, 3 ] // broadcast compatible shape
};
var out = array( opts );
map.assign( arr, out, naryFunction( abs, 1 ) );
var v = out.get( 0, 1, 1 );
// returns 5
v = out.get( 1, 1, 1 );
// returns 5In general, avoid providing output ndarray-like objects which are non-contiguous views containing one or more elements referring to the same memory location. Writing to an overlapping non-contiguous view is likely to simultaneously affect multiple elements and yield unexpected results.
The applied function is provided the same arguments as with map.
-
The
mapfunction always returns an output value having a "generic" data type. For example, if provided an array-like object, the function returns a genericarray. If provided anndarray, the function returns anndarrayhaving a "generic" data type.Accordingly, in contrast to
TypedArray.prototype.map(), when provided a typed array, themapfunction does not return a typed array of the same type. To assign results to a typed array, use themap.assignmethod. -
Both
mapandmap.assignaccept array-like objects exposing getters and setters for array element access (e.g.,Complex64Array,Complex128Array, etc).import Complex64Array from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-complex64@deno/mod.js'; import Complex64 from 'https://cdn.jsdelivr.net/gh/stdlib-js/complex-float32-ctor@deno/mod.js'; import realf from 'https://cdn.jsdelivr.net/gh/stdlib-js/complex-float32-real@deno/mod.js'; import imagf from 'https://cdn.jsdelivr.net/gh/stdlib-js/complex-float32-imag@deno/mod.js'; function scale( z ) { return new Complex64( realf(z)*10.0, imagf(z)*10.0 ); } var x = new Complex64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 ] ); var y = new Complex64Array( 4 ); map.assign( x, y, scale ); var v = y.get( 0 ); var re = realf( v ); // returns 10.0 var im = imagf( v ); // returns 20.0
-
When applying a function to
ndarray-like objects, performance will be best forndarray-like objects which are single-segment contiguous. For non-contiguous arrays, see@stdlib/ndarray-base/unary. -
Both
mapandmap.assigndo not skipundefinedelements.
import filledarrayBy from 'https://cdn.jsdelivr.net/gh/stdlib-js/array-filled-by@deno/mod.js';
var discreteUniform = require( 'https://cdn.jsdelivr.net/gh/stdlib-js/random-base-discrete-uniform' ).factory;
import naryFunction from 'https://cdn.jsdelivr.net/gh/stdlib-js/utils-nary-function@deno/mod.js';
import abs2 from 'https://cdn.jsdelivr.net/gh/stdlib-js/math-base-special-abs2@deno/mod.js';
import array from 'https://cdn.jsdelivr.net/gh/stdlib-js/ndarray-array@deno/mod.js';
import map from 'https://cdn.jsdelivr.net/gh/stdlib-js/utils-map@deno/mod.js';
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 f = naryFunction( abs2, 1 );
// Compute the element-wise squared absolute value...
var y = map( x, f );
console.log( 'x:' );
console.log( x.data );
console.log( 'y:' );
console.log( y.data );@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-reduce: apply a function against an accumulator and each element in an array and return the accumulated result.
This package is part of stdlib, a standard library 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.
