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stdlib/lib/node_modules/@stdlib/utils/map2d at develop · stdlib-js/stdlib

Apply a function to each nested element in an array of arrays and assign the result to a nested element in a new array of arrays.

Usage

var map2d = require( '@stdlib/utils/map2d' );

map2d( arr, fcn[, thisArg] )

Applies a function to each nested element in an array of arrays and assigns the result to a nested element in a new array of arrays.

var naryFunction = require( '@stdlib/utils/nary-function' );
var abs = require( '@stdlib/math/base/special/abs' );

var arr = [
    [ -1, -2, -3 ],
    [ -4, -5, -6 ]
];

var out = map2d( arr, naryFunction( abs, 1 ) );
// returns [ [ 1, 2, 3 ], [ 4, 5, 6 ] ]

The applied function is provided the following arguments:

  • value: array element.
  • indices: current array element indices.
  • arr: input array.

To set the this context when invoking the input function, provide a thisArg.

var abs = require( '@stdlib/math/base/special/abs' );

function fcn( v ) {
    this.count += 1;
    return abs( v );
}

var arr = [
    [ -1, -2, -3 ],
    [ -4, -5, -6 ]
];

var ctx = {
    'count': 0
};

var out = map2d( arr, fcn, ctx );
// returns [ [ 1, 2, 3 ], [ 4, 5, 6 ] ]

var cnt = ctx.count;
// returns 6

Examples

var filledarrayBy = require( '@stdlib/array/filled-by' );
var discreteUniform = require( '@stdlib/random/base/discrete-uniform' ).factory;
var naryFunction = require( '@stdlib/utils/nary-function' );
var abs2 = require( '@stdlib/math/base/special/abs2' );
var map2d = require( '@stdlib/utils/map2d' );

function fill( i ) {
    var rand = discreteUniform( -10*(i+1), 10*(i+1) );
    return filledarrayBy( 10, 'float64', rand );
}

// Create a nested array of arrays:
var x = filledarrayBy( 10, 'generic', fill );

// Create an explicit unary function:
var f = naryFunction( abs2, 1 );

// Compute the element-wise squared absolute value...
var y = map2d( x, f );

console.log( 'x:' );
console.log( x );

console.log( 'y:' );
console.log( y );

See Also

  • @stdlib/utils/map: apply a function to each element in an array and assign the result to an element in an output array.
  • @stdlib/utils/map3d: apply a function to each nested element in a three-dimensional nested array and assign the result to a nested element in a new three-dimensional nested array.
  • @stdlib/utils/map4d: apply a function to each nested element in a four-dimensional nested array and assign the result to a nested element in a new four-dimensional nested array.
  • @stdlib/utils/map5d: apply a function to each nested element in a five-dimensional nested array and assign the result to a nested element in a new five-dimensional nested array.
  • @stdlib/utils/reduce2d: reduce the number of dimensions by one of a two-dimensional nested array by applying a function against an accumulator and each element along the innermost dimension and returning the accumulation results as a one-dimensional array.