Hypergeometric Random Numbers

Usage

var hypergeometric = require( '@stdlib/random/base/hypergeometric' );

hypergeometric( N, K, n )

Returns a pseudorandom number drawn from a hypergeometric distribution with parameters N (population size), K (subpopulation size), and n (number of draws).

var r = hypergeometric( 20, 10, 7 );
// returns <number>

N, K, and n must all be nonnegative integers; otherwise, the function returns NaN.

var r = hypergeometric( 10.5, 10, 10 );
// returns NaN

r = hypergeometric( 10, 4.4, 2 );
// returns NaN

r = hypergeometric( 10, 5, -1 );
// returns NaN

r = hypergeometric( NaN, NaN, NaN );
// returns NaN

If n > N or K > N, the function returns NaN.

var r = hypergeometric( 7, 5, 12 );
// returns NaN

hypergeometric.factory( [N, K, n, ][options] )

Returns a pseudorandom number generator (PRNG) for generating pseudorandom numbers drawn from a hypergeometric distribution.

var rand = hypergeometric.factory();

var r = rand( 20, 10, 15 );
// returns <number>

If provided N, K, and n, the returned generator returns random variates from the specified distribution.

var rand = hypergeometric.factory( 20, 10, 15 );

var r = rand();
// returns <number>

r = rand();
// returns <number>

If not provided N, K, and n, the returned generator requires that all three parameters be specified at each invocation.

var rand = hypergeometric.factory();

var r = rand( 10, 7, 3 );
// returns <number>

r = rand( 104, 48, 21 );
// returns <number>

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 returned pseudorandom number generator, one must seed the provided prng (assuming the provided prng is seedable).
• seed: pseudorandom number generator seed.
• state: a Uint32Array 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 a returned 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.

var minstd = require( '@stdlib/random/base/minstd' );

var rand = hypergeometric.factory({
    'prng': minstd.normalized
});

var r = rand( 10, 8, 5 );
// returns <number>

To seed a pseudorandom number generator, set the seed option.

var rand1 = hypergeometric.factory({
    'seed': 12345
});

var r1 = rand1( 10, 8, 5 );
// returns <number>

var rand2 = hypergeometric.factory( 10, 8, 5, {
    'seed': 12345
});

var r2 = rand2();
// returns <number>

var bool = ( r1 === r2 );
// returns true

To return a generator having a specific initial state, set the generator state option.

var rand;
var bool;
var r;
var i;

// Generate pseudorandom numbers, thus progressing the generator state:
for ( i = 0; i < 1000; i++ ) {
    r = hypergeometric( 10, 8, 5 );
}

// Create a new PRNG initialized to the current state of `hypergeometric`:
rand = hypergeometric.factory({
    'state': hypergeometric.state
});

// Test that the generated pseudorandom numbers are the same:
bool = ( rand( 10, 8, 5 ) === hypergeometric( 10, 8, 5 ) );
// returns true

hypergeometric.NAME

The generator name.

var str = hypergeometric.NAME;
// returns 'hypergeometric'

hypergeometric.PRNG

The underlying pseudorandom number generator.

var prng = hypergeometric.PRNG;
// returns <Function>

hypergeometric.seed

The value used to seed hypergeometric().

var rand;
var r;
var i;

// Generate pseudorandom values...
for ( i = 0; i < 100; i++ ) {
    r = hypergeometric( 20, 10, 15 );
}

// Generate the same pseudorandom values...
rand = hypergeometric.factory( 20, 10, 15, {
    'seed': hypergeometric.seed
});
for ( i = 0; i < 100; i++ ) {
    r = rand();
}

If provided a PRNG for uniformly distributed numbers, this value is null.

var rand = hypergeometric.factory({
    'prng': Math.random
});

var seed = rand.seed;
// returns null

hypergeometric.seedLength

Length of generator seed.

var len = hypergeometric.seedLength;
// returns <number>

If provided a PRNG for uniformly distributed numbers, this value is null.

var rand = hypergeometric.factory({
    'prng': Math.random
});

var len = rand.seedLength;
// returns null

hypergeometric.state

Writable property for getting and setting the generator state.

var r = hypergeometric( 10, 8, 5 );
// returns <number>

r = hypergeometric( 10, 8, 5 );
// returns <number>

// ...

// Get a copy of the current state:
var state = hypergeometric.state;
// returns <Uint32Array>

r = hypergeometric( 10, 8, 5 );
// returns <number>

r = hypergeometric( 10, 8, 5 );
// returns <number>

// Reset the state:
hypergeometric.state = state;

// Replay the last two pseudorandom numbers:
r = hypergeometric( 10, 8, 5 );
// returns <number>

r = hypergeometric( 10, 8, 5 );
// returns <number>

// ...

If provided a PRNG for uniformly distributed numbers, this value is null.

var rand = hypergeometric.factory({
    'prng': Math.random
});

var state = rand.state;
// returns null

hypergeometric.stateLength

Length of generator state.

var len = hypergeometric.stateLength;
// returns <number>

If provided a PRNG for uniformly distributed numbers, this value is null.

var rand = hypergeometric.factory({
    'prng': Math.random
});

var len = rand.stateLength;
// returns null

hypergeometric.byteLength

Size (in bytes) of generator state.

var sz = hypergeometric.byteLength;
// returns <number>

If provided a PRNG for uniformly distributed numbers, this value is null.

var rand = hypergeometric.factory({
    'prng': Math.random
});

var sz = rand.byteLength;
// returns null

hypergeometric.toJSON()

Serializes the pseudorandom number generator as a JSON object.

var o = hypergeometric.toJSON();
// returns { 'type': 'PRNG', 'name': '...', 'state': {...}, 'params': [] }

If provided a PRNG for uniformly distributed numbers, this method returns null.

var rand = hypergeometric.factory({
    'prng': Math.random
});

var o = rand.toJSON();
// returns null