@stdlib/math-strided-special-dcbrt-by NPM

dcbrtBy

$NPM version$ $Build Status$ $Coverage Status$

Compute the cube root of each element retrieved from a double-precision floating-point strided array via a callback function.

Installation

npm install @stdlib/math-strided-special-dcbrt-by

Usage

var dcbrtBy = require( '@stdlib/math-strided-special-dcbrt-by' );

dcbrtBy( N, x, strideX, y, strideY, clbk[, thisArg] )

Computes the cube root of each element retrieved from an input double-precision floating-point strided array via a callback function and assigns each result to an element in an output double-precision floating-point strided array.

var Float64Array = require( '@stdlib/array-float64' );

function accessor( v ) {
    return v;
}

var x = new Float64Array( [ 1.0, 9.0, -27.0, 81.0, -125.0 ] );
var out = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0 ] );

dcbrtBy( x.length, x, 1, out, 1, accessor );
// out => <Float64Array>[ 1.0, ~2.08, -3.0, ~4.327, -5.0 ]

The function accepts the following arguments:

N: number of indexed elements.
x: input Float64Array.
strideX: index increment for x.
y: output Float64Array.
strideY: index increment for y.
clbk: callback function.
thisArg: execution context (optional).

The invoked callback function is provided four arguments:

value: input array element.
idx: iteration index (zero-based).
indices: input and output array strided indices [ix, iy] (computed according to offset + idx*stride).
arrays: input and output arrays [x, y].

To set the callback execution context, provide a thisArg.

var Float64Array = require( '@stdlib/array-float64' );

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

var context = {
    'count': 0
};

var x = new Float64Array( [ 1.0, 9.0, -27.0, 81.0, -125.0 ] );
var out = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0 ] );

dcbrtBy( x.length, x, 1, out, 1, accessor, context );
// out => <Float64Array>[ 1.0, ~2.08, -3.0, ~4.327, -5.0 ]

var cnt = context.count;
// returns 5

The N and stride parameters determine which strided array elements are accessed at runtime. For example, to index every other value in x and to index the first N elements of y in reverse order,

var Float64Array = require( '@stdlib/array-float64' );

function accessor( v ) {
    return v;
}

var x = new Float64Array( [ 1.0, 9.0, -27.0, 81.0, -125.0, -9.14 ] );
var out = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

dcbrtBy( 3, x, 2, out, -1, accessor );
// out => <Float64Array>[ -5.0, -3.0, 1.0, 0.0, 0.0, 0.0 ]

Note that indexing is relative to the first index. To introduce an offset, use typed array views.

var Float64Array = require( '@stdlib/array-float64' );

function accessor( v ) {
    return v;
}

// Initial arrays...
var x0 = new Float64Array( [ 1.0, 9.0, -27.0, 81.0, -125.0, -9.14 ] );
var out0 = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

// Create offset views...
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var out1 = new Float64Array( out0.buffer, out0.BYTES_PER_ELEMENT*3 ); // start at 4th element

dcbrtBy( 3, x1, -2, out1, 1, accessor );
// out0 => <Float64Array>[ 0.0, 0.0, 0.0, ~-2.091, ~4.327, ~2.08 ]

dcbrtBy.ndarray( N, x, strideX, offsetX, y, strideY, offsetY, clbk[, thisArg] )

var Float64Array = require( '@stdlib/array-float64' );

function accessor( v ) {
    return v;
}

var x = new Float64Array( [ 1.0, 9.0, -27.0, 81.0, -125.0 ] );
var out = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0 ] );

dcbrtBy.ndarray( x.length, x, 1, 0, out, 1, 0, accessor );
// out => <Float64Array>[ 1.0, ~2.08, -3.0, ~4.327, -5.0 ]

The function accepts the following additional arguments:

offsetX: starting index for x.
offsetY: starting index for y.

While typed array views mandate a view offset based on the underlying buffer, the offset parameters support indexing semantics based on starting indices. For example, to index every other value in x starting from the second value and to index the last N elements in y,

var Float64Array = require( '@stdlib/array-float64' );

function accessor( v ) {
    return v;
}

var x = new Float64Array( [ 1.0, 9.0, -27.0, 81.0, -125.0, -9.14 ] );
var out = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

dcbrtBy.ndarray( 3, x, 2, 1, out, -1, out.length-1, accessor );
// out => <Float64Array>[ 0.0, 0.0, 0.0, ~-2.091, ~4.327, ~2.08 ]

Notes

If a provided callback function does not return any value (or equivalently, explicitly returns undefined), the value is ignored.

var Float64Array = require( '@stdlib/array-float64' );

function accessor() {
    // No-op...
}

var x = new Float64Array( [ 1.0, 9.0, -27.0, 81.0, -125.0 ] );
var out = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0 ] );

dcbrtBy( x.length, x, 1, out, 1, accessor );
// out => <Float64Array>[ 0.0, 0.0, 0.0, 0.0, 0.0 ]

Examples

var uniform = require( '@stdlib/random-base-uniform' ).factory;
var filledarray = require( '@stdlib/array-filled' );
var filledarrayBy = require( '@stdlib/array-filled-by' );
var dcbrtBy = require( '@stdlib/math-strided-special-dcbrt-by' );

function accessor( v, i ) {
    if ( (i%3) === 0 ) {
        // Simulate a "missing" value...
        return;
    }
    return v;
}

var x = filledarrayBy( 10, 'float64', uniform( -10.0, 10.0 ) );
console.log( x );

var out = filledarray( null, 10, 'float64' );
console.log( out );

dcbrtBy.ndarray( x.length, x, 1, 0, out, -1, out.length-1, accessor );
console.log( out );

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.