@stdlib/array/base/broadcast-array/README.md

Arrays.

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# broadcastArray

> Broadcast an array to a specified shape.

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## Usage

```javascript
var broadcastArray = require( '@stdlib/array/base/broadcast-array' );
```

#### broadcastArray( x, inShape, outShape )

Broadcasts an array to a specified shape.

```javascript
var x = [ 1, 2 ];

var out = broadcastArray( x, [ 2 ], [ 2, 2 ] );
// returns {...}

var shape = out.shape;
// returns [ 2, 2 ]

var strides = out.strides;
// returns [ 0, 1 ]

var ref = out.ref;
// returns [ 1, 2 ]

var bool = ( x === ref );
// returns true

var data = out.data;
// returns [ [ 1, 2 ] ]
```

The function returns an object having the following properties:

-   **ref**: reference to the original input array.
-   **data**: broadcasted array.
-   **shape**: broadcasted array shape.
-   **strides**: broadcasted array strides. Strides describe how to iterate over broadcasted array dimensions.

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## Notes

-   The broadcasted array shares the same data as the input array. As more than one element of a broadcasted array may refer to the same memory location, writing to the broadcasted array may affect multiple elements. If you need to write to the broadcasted array, copy the array **before** performing operations which may mutate elements.
-   The function throws an error if a provided input shape is [incompatible][@stdlib/ndarray/base/broadcast-shapes] with a provided output shape.

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## Examples

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

```javascript
var broadcastArray = require( '@stdlib/array/base/broadcast-array' );

// Create a 2x1 array:
var x = [
    [ 1 ],
    [ 2 ]
];

// Broadcast the array to 3x2x4:
var o = broadcastArray( x, [ 2, 1 ], [ 3, 2, 4 ] );
// returns {...}

// Retrieve the shape:
var sh = o.shape;
// returns [ 3, 2, 4 ]

// Retrieve the array "strides":
var st = o.strides;
// returns [...]

// Initialize loop indices:
var i0 = 0;
var i1 = 0;
var i2 = 0;

// Iterate over elements in the broadcasted array...
var i;
var j;
var k;
for ( i = 0; i < sh[ 0 ]; i++ ) {
    i1 = 0;
    for ( j = 0; j < sh[ 1 ]; j++ ) {
        i2 = 0;
        for ( k = 0; k < sh[ 2 ]; k++ ) {
            console.log( 'y[%s] = %d', [ i, j, k ].join( ',' ), o.data[ i0 ][ i1 ][ i2 ] );
            i2 += st[ 2 ];
        }
        i1 += st[ 1 ];
    }
    i0 += st[ 0 ];
}
```

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[@stdlib/ndarray/base/broadcast-shapes]: https://www.npmjs.com/package/@stdlib/ndarray-base-broadcast-shapes

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