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<!-- lint disable maximum-heading-length -->

# dcbrtBy

> Compute the [cube root][@stdlib/math/base/special/cbrt] of each element retrieved from a double-precision floating-point strided array via a callback function.

<section class="intro">

</section>

<!-- /.intro -->

<section class="usage">

## Usage

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

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

Computes the [cube root][@stdlib/math/base/special/cbrt] 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.

```javascript
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`][@stdlib/array/float64].
-   **strideX**: index increment for `x`.
-   **y**: output [`Float64Array`][@stdlib/array/float64].
-   **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`.

```javascript
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,

```javascript
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`][@stdlib/array/float64] views.

```javascript
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] )

Computes the [cube root][@stdlib/math/base/special/cbrt] 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 using alternative indexing semantics.

```javascript
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`][@stdlib/array/float64] 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`,

```javascript
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 ]
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

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

    ```javascript
    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 ]
    ```

</section>

<!-- /.notes -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
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 );
```

</section>

<!-- /.examples -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/math/strided/special/cbrt`][@stdlib/math/strided/special/cbrt]</span><span class="delimiter">: </span><span class="description">compute the cube root of each element in a strided array.</span>

</section>

<!-- /.related -->

<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="links">

[@stdlib/array/float64]: https://www.npmjs.com/package/@stdlib/array-float64

[@stdlib/math/base/special/cbrt]: https://github.com/stdlib-js/math/tree/main/base/special/cbrt

<!-- <related-links> -->

[@stdlib/math/strided/special/cbrt]: https://github.com/stdlib-js/math/tree/main/strided/special/cbrt

<!-- </related-links> -->

</section>

<!-- /.links -->
