dcbrtBy

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

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 );