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feat: add random/strided/geometric
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Closes: #887
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# Geometric Random Numbers

> Fill a strided array with pseudorandom numbers drawn from a [geometric][@stdlib/random/base/geometric] distribution.
<section class="usage">

## Usage

```javascript
var geometric = require( '@stdlib/random/strided/geometric' );
```

#### geometric( N, p, sp, out, so )

Fills a strided array with pseudorandom numbers drawn from a [geometric][@stdlib/random/base/geometric] distribution.

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

// Create an array:
var out = new Float64Array( 10 );

// Fill the array with pseudorandom numbers:
geometric( out.length, [ 0.01 ], 0, out, 1 );
```

The function has the following parameters:

- **N**: number of indexed elements.
- **p**: rate parameter.
- **sp**: index increment for `p`.
- **out**: output array.
- **so**: index increment for `out`.

The `N` and stride parameters determine which strided array elements are accessed at runtime. For example, to access every other value in `out`,

```javascript
var out = [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ];

geometric( 3, [ 0.01 ], 0, out, 2 );
```

Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views.

<!-- eslint-disable stdlib/capitalized-comments -->

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

// Initial array:
var p0 = new Float64Array( [ 0.01, 0.01, 0.01, 0.01, 0.01, 0.01 ] );

// Create offset view:
var p1 = new Float64Array( p0.buffer, p0.BYTES_PER_ELEMENT*3 ); // start at 4th element

// Create an output array:
var out = new Float64Array( 3 );

// Fill the output array:
geometric( out.length, p1, -1, out, 1 );
```

#### geometric.ndarray( N, p, sp, op, out, so, oo )

Fills a strided array with pseudorandom numbers drawn from a [geometric][@stdlib/random/base/geometric] distribution using alternative indexing semantics.

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

// Create an array:
var out = new Float64Array( 10 );

// Fill the array with pseudorandom numbers:
geometric.ndarray( out.length, [ 0.01 ], 0, 0, out, 1, 0 );
```

The function has the following additional parameters:

- **op**: starting index for `p`.
- **oo**: starting index for `out`.

While [`typed array`][mdn-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 access every other value in `out` starting from the second value,

```javascript
var out = [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ];

geometric.ndarray( 3, [ 0.01 ], 0, 0, out, 2, 1 );
```

#### geometric.factory( \[options] )

Returns a function for filling strided arrays with pseudorandom numbers drawn from a [geometric][@stdlib/random/base/geometric] distribution.

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

var random = geometric.factory();
// returns <Function>

// Create an array:
var out = new Float64Array( 10 );

// Fill the array with pseudorandom numbers:
random( out.length, [ 0.01 ], 0, out, 1 );
```

The function accepts the following `options`:

- **prng**: pseudorandom number generator for generating uniformly distributed pseudorandom numbers on the interval `[0,1)`. If provided, the function **ignores** both the `state` and `seed` options. In order to seed the underlying pseudorandom number generator, one must seed the provided `prng` (assuming the provided `prng` is seedable).
- **seed**: pseudorandom number generator seed.
- **state**: a [`Uint32Array`][@stdlib/array/uint32] containing pseudorandom number generator state. If provided, the function ignores the `seed` option.
- **copy**: `boolean` indicating whether to copy a provided pseudorandom number generator state. Setting this option to `false` allows sharing state between two or more pseudorandom number generators. Setting this option to `true` ensures that an underlying generator has exclusive control over its internal state. Default: `true`.

To use a custom PRNG as the underlying source of uniformly distributed pseudorandom numbers, set the `prng` option.

```javascript
var Float64Array = require( '@stdlib/array/float64' );
var minstd = require( '@stdlib/random/base/minstd' );

var opts = {
'prng': minstd.normalized
};
var random = geometric.factory( opts );

var out = new Float64Array( 10 );
random( out.length, [ 0.01 ], 0, out, 1 );
```

To seed the underlying pseudorandom number generator, set the `seed` option.

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

var opts = {
'seed': 12345
};
var random = geometric.factory( opts );

var out = new Float64Array( 10 );
random( out.length, [ 0.01 ], 0, out, 1 );
```

* * *

#### random.PRNG

The underlying pseudorandom number generator.

```javascript
var prng = geometric.PRNG;
// returns <Function>
```

#### geometric.seed

The value used to seed the underlying pseudorandom number generator.

```javascript
var seed = geometric.seed;
// returns <Uint32Array>
```

If the `factory` method is provided a PRNG for uniformly distributed numbers, the associated property value on the returned function is `null`.

```javascript
var minstd = require( '@stdlib/random/base/minstd-shuffle' ).normalized;

var random = geometric.factory({
'prng': minstd
});
// returns <Function>

var seed = random.seed;
// returns null
```

#### geometric.seedLength

Length of underlying pseudorandom number generator seed.

```javascript
var len = geometric.seedLength;
// returns <number>
```

If the `factory` method is provided a PRNG for uniformly distributed numbers, the associated property value on the returned function is `null`.

```javascript
var minstd = require( '@stdlib/random/base/minstd-shuffle' ).normalized;

var random = geometric.factory({
'prng': minstd
});
// returns <Function>

var len = random.seedLength;
// returns null
```

#### geometric.state

Writable property for getting and setting the underlying pseudorandom number generator state.

```javascript
var state = geometric.state;
// returns <Uint32Array>
```

If the `factory` method is provided a PRNG for uniformly distributed numbers, the associated property value on the returned function is `null`.

```javascript
var minstd = require( '@stdlib/random/base/minstd-shuffle' ).normalized;

var random = geometric.factory({
'prng': minstd
});
// returns <Function>

var state = random.state;
// returns null
```

#### geometric.stateLength

Length of underlying pseudorandom number generator state.

```javascript
var len = geometric.stateLength;
// returns <number>
```

If the `factory` method is provided a PRNG for uniformly distributed numbers, the associated property value on the returned function is `null`.

```javascript
var minstd = require( '@stdlib/random/base/minstd-shuffle' ).normalized;

var random = geometric.factory({
'prng': minstd
});
// returns <Function>

var len = random.stateLength;
// returns null
```

#### geometric.byteLength

Size (in bytes) of underlying pseudorandom number generator state.

```javascript
var sz = geometric.byteLength;
// returns <number>
```

If the `factory` method is provided a PRNG for uniformly distributed numbers, the associated property value on the returned function is `null`.

```javascript
var minstd = require( '@stdlib/random/base/minstd-shuffle' ).normalized;

var random = geometric.factory({
'prng': minstd
});
// returns <Function>

var sz = random.byteLength;
// returns null
```

</section>

<!-- /.usage -->

<section class="notes">

* * *

## Notes

- If `N <= 0`, both `geometric` and `geometric.ndarray` leave the output array unchanged.
- Both `geometric` and `geometric.ndarray` support array-like objects having getter and setter accessors for array element access.

</section>

<!-- /.notes -->

<section class="examples">

* * *

## Examples

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

```javascript
var zeros = require( '@stdlib/array/zeros' );
var zeroTo = require( '@stdlib/array/zero-to' );
var logEach = require( '@stdlib/console/log-each' );
var geometric = require( '@stdlib/random/strided/geometric' );

// Specify a PRNG seed:
var opts = {
'seed': 1234
};

// Create a seeded PRNG:
var rand1 = geometric.factory( opts );

// Create an array:
var x1 = zeros( 10, 'float64' );

// Fill the array with pseudorandom numbers:
rand1( x1.length, [ 0.01 ], 0, x1, 1 );

// Create another function for filling strided arrays:
var rand2 = geometric.factory( opts );
// returns <Function>

// Create a second array:
var x2 = zeros( 10, 'generic' );

// Fill the array with the same pseudorandom numbers:
rand2( x2.length, [ 0.01 ], 0, x2, 1 );

// Create a list of indices:
var idx = zeroTo( x1.length, 'generic' );

// Print the array contents:
logEach( 'x1[%d] = %.2f; x2[%d] = %.2f', idx, x1, idx, x2 );
```

</section>

<!-- /.examples -->

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

<section class="related">

</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">

[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray

[@stdlib/random/base/geometric]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/random/base/geometric

[@stdlib/array/uint32]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/uint32

</section>

<!-- /.links -->
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