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Create a readable stream for generating pseudorandom numbers drawn from a standard normal distribution.
npm install @stdlib/random-streams-randn
Alternatively,
- To load the package in a website via a
script
tag without installation and bundlers, use the ES Module available on theesm
branch (see README). - If you are using Deno, visit the
deno
branch (see README for usage intructions). - For use in Observable, or in browser/node environments, use the Universal Module Definition (UMD) build available on the
umd
branch (see README). - To use as a general utility for the command line, install the corresponding CLI package globally.
The branches.md file summarizes the available branches and displays a diagram illustrating their relationships.
To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.
var randomStream = require( '@stdlib/random-streams-randn' );
Returns a readable stream for generating pseudorandom numbers drawn from a standard normal distribution.
var inspectStream = require( '@stdlib/streams-node-inspect-sink' );
var iStream;
var stream;
function log( chunk, idx ) {
console.log( chunk.toString() );
if ( idx === 10 ) {
stream.destroy();
}
}
stream = randomStream();
iStream = inspectStream( log );
stream.pipe( iStream );
The function accepts the following options
:
-
objectMode: specifies whether a stream should operate in objectMode. Default:
false
. -
encoding: specifies how
Buffer
objects should be decoded tostrings
. Default:null
. -
highWaterMark: specifies the maximum number of bytes to store in an internal buffer before ceasing to generate additional pseudorandom numbers.
-
sep: separator used to join streamed data. This option is only applicable when a stream is not in objectMode. Default:
'\n'
. -
iter: number of iterations.
-
name: name of a supported pseudorandom number generator (PRNG), which will serve as the underlying source of pseudorandom numbers. The following PRNGs are supported:
improved-ziggurat
: improved ziggurat method.box-muller
: Box-Muller transform.
Default:
'improved-ziggurat'
. -
prng: pseudorandom number generator for generating uniformly distributed pseudorandom numbers on the interval
[0,1)
. If provided, the function ignores both thestate
andseed
options. In order to seed the returned iterator, one must seed the providedprng
(assuming the providedprng
is seedable). -
seed: pseudorandom number generator seed.
-
state: a
Uint32Array
containing pseudorandom number generator state. If provided, the function ignores theseed
option. -
copy:
boolean
indicating whether to copy a provided pseudorandom number generator state. Setting this option tofalse
allows sharing state between two or more pseudorandom number generators and/or streams. Setting this option totrue
ensures that a stream generator has exclusive control over its internal state. Default:true
. -
siter: number of iterations after which to emit the pseudorandom number generator state. This option is useful when wanting to deterministically capture a stream's underlying PRNG state. Default:
1e308
.
To set stream options
,
var opts = {
'objectMode': true,
'encoding': 'utf8',
'highWaterMark': 64
};
var stream = randomStream( opts );
By default, the function returns a stream which can generate an infinite number of values (i.e., the stream will never end). To limit the number of generated pseudorandom numbers, set the iter
option.
var inspectStream = require( '@stdlib/streams-node-inspect-sink' );
function log( chunk ) {
console.log( chunk.toString() );
}
var opts = {
'iter': 10
};
var stream = randomStream( opts );
var iStream = inspectStream( log );
stream.pipe( iStream );
By default, when not operating in objectMode, a returned stream delineates generated pseudorandom numbers using a newline character. To specify an alternative separator, set the sep
option.
var inspectStream = require( '@stdlib/streams-node-inspect-sink' );
function log( chunk ) {
console.log( chunk.toString() );
}
var opts = {
'iter': 10,
'sep': ','
};
var stream = randomStream( opts );
var iStream = inspectStream( log );
stream.pipe( iStream );
By default, the underlying pseudorandom number generator is improved-ziggurat
. To use a different PRNG, set the name
option.
var opts = {
'name': 'box-muller'
};
var stream = randomStream( opts );
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 opts = {
'prng': minstd.normalized
};
var stream = randomStream( opts );
To seed the underlying pseudorandom number generator, set the seed
option.
var inspectStream = require( '@stdlib/streams-node-inspect-sink' );
function log( v ) {
console.log( v );
}
var opts = {
'name': 'improved-ziggurat',
'objectMode': true,
'iter': 10,
'seed': 1234
};
var stream = randomStream( opts );
opts = {
'objectMode': true
};
var iStream = inspectStream( opts, log );
stream.pipe( iStream );
To return a readable stream with an underlying pseudorandom number generator having a specific initial state, set the state
option.
var inspectStream = require( '@stdlib/streams-node-inspect-sink' );
function log( v ) {
console.log( v );
}
var opts1 = {
'name': 'improved-ziggurat',
'objectMode': true,
'iter': 10
};
var stream = randomStream( opts1 );
var opts2 = {
'objectMode': true
};
var iStream = inspectStream( opts2, log );
// Stream pseudorandom numbers, thus progressing the underlying generator state:
stream.pipe( iStream );
// Create a new PRNG stream initialized to the last state of the previous stream:
var opts3 = {
'name': 'improved-ziggurat',
'objectMode': true,
'iter': 10,
'state': stream.state
};
stream = randomStream( opts3 );
iStream = inspectStream( opts2, log );
// Stream pseudorandom numbers starting from the last state of the previous stream:
stream.pipe( iStream );
The value used to seed the underlying pseudorandom number generator.
var stream = randomStream();
var seed = stream.seed;
If provided a PRNG for uniformly distributed numbers, this value is null
.
var minstd = require( '@stdlib/random-base-minstd-shuffle' ).normalized;
var stream = randomStream({
'prng': minstd
});
var seed = stream.seed;
// returns null
Length of underlying pseudorandom number generator seed.
var stream = randomStream();
var len = stream.seedLength;
// returns <number>
If provided a PRNG for uniformly distributed numbers, this value is null
.
var minstd = require( '@stdlib/random-base-minstd-shuffle' ).normalized;
var stream = randomStream({
'prng': minstd
});
var len = stream.seedLength;
// returns null
Writable property for getting and setting the underlying pseudorandom number generator state.
var stream = randomStream();
var state = stream.state;
If provided a PRNG for uniformly distributed numbers, this value is null
.
var minstd = require( '@stdlib/random-base-minstd-shuffle' ).normalized;
var stream = randomStream({
'prng': minstd
});
var state = stream.state;
// returns null
Length of underlying pseudorandom number generator state.
var stream = randomStream();
var len = stream.stateLength;
// returns <number>
If provided a PRNG for uniformly distributed numbers, this value is null
.
var minstd = require( '@stdlib/random-base-minstd-shuffle' ).normalized;
var stream = randomStream({
'prng': minstd
});
var len = stream.stateLength;
// returns null
Size (in bytes) of underlying pseudorandom number generator state.
var stream = randomStream();
var sz = stream.byteLength;
// returns <number>
If provided a PRNG for uniformly distributed numbers, this value is null
.
var minstd = require( '@stdlib/random-base-minstd-shuffle' ).normalized;
var stream = randomStream({
'prng': minstd
});
var sz = stream.byteLength;
// returns null
Returns a function
for creating readable streams which generate pseudorandom numbers drawn from a standard normal distribution.
var opts = {
'objectMode': true,
'encoding': 'utf8',
'highWaterMark': 64
};
var createStream = randomStream.factory( opts );
The method accepts the same options
as randomStream()
.
This method is a convenience function to create streams which always operate in objectMode.
var inspectStream = require( '@stdlib/streams-node-inspect-sink' );
function log( v ) {
console.log( v );
}
var opts = {
'iter': 10
};
var stream = randomStream.objectMode( opts );
opts = {
'objectMode': true
};
var iStream = inspectStream( opts, log );
stream.pipe( iStream );
This method accepts the same options
as randomStream()
; however, the method will always override the objectMode
option in options
.
In addition to the standard readable stream events, the following events are supported...
Emitted after internally generating siter
pseudorandom numbers.
var opts = {
'siter': 10 // emit the PRNG state every 10 pseudorandom numbers
};
var stream = randomStream( opts );
stream.on( 'state', onState );
function onState( state ) {
// Do something with the emitted state, such as save to file...
}
- Warning: the default underlying source of pseudorandom numbers may change in the future. If exact reproducibility is required, either explicitly specify a PRNG via the
name
option or use an underlying PRNG directly. - If PRNG state is "shared" (meaning a state array was provided during stream creation and not copied) and one sets the generator state to a state array having a different length, the underlying PRNG does not update the existing shared state and, instead, points to the newly provided state array. In order to synchronize PRNG output according to the new shared state array, the state array for each relevant PRNG must be explicitly set.
- If PRNG state is "shared" and one sets the generator state to a state array of the same length, the PRNG state is updated (along with the state of all other PRNGs sharing the PRNG's state array).
- In order to capture the PRNG state after a specific number of generated pseudorandom numbers, regardless of internal stream buffering, use the
siter
option in conjunction with astate
event listener. Attempting to capture the underlying PRNG state after reading generated numbers is not likely to give expected results, as internal stream buffering will mean more values have been generated than have been read. Thus, the state returned by thestate
property will likely reflect a future PRNG state from the perspective of downstream consumers.
var inspectStream = require( '@stdlib/streams-node-inspect-sink' );
var randomStream = require( '@stdlib/random-streams-randn' );
function log( v ) {
console.log( v.toString() );
}
var opts = {
'objectMode': true,
'iter': 10
};
var stream = randomStream( opts );
opts = {
'objectMode': true
};
var iStream = inspectStream( opts, log );
stream.pipe( iStream );
To use as a general utility, install the CLI package globally
npm install -g @stdlib/random-streams-randn-cli
Usage: random-randn [options]
Options:
-h, --help Print this message.
-V, --version Print the package version.
--sep sep Separator used to join streamed data. Default: '\n'.
-n, --iter iterations Number of pseudorandom numbers.
--name name Pseudorandom number generator name. Default:
'improved-ziggurat'.
--seed seed Pseudorandom number generator seed.
--state filepath Path to a file containing the pseudorandom number
generator state.
--snapshot filepath Output file path for saving the pseudorandom number
generator state upon exit.
- In accordance with POSIX convention, a trailing newline is always appended to generated output prior to exit.
- Specifying a "snapshot" file path is useful when wanting to resume pseudorandom number generation due to, e.g., a downstream failure in an analysis pipeline. Before exiting, the process will store the pseudorandom number generator state in a file specified according to a provided file path. Upon loading a snapshot (state), the process will generate pseudorandom numbers starting from the loaded state, thus avoiding having to seed and replay an entire analysis.
$ random-randn -n 10 --name improved-ziggurat --seed 1234
@stdlib/random-base/randn
: standard normal pseudorandom numbers.@stdlib/random-iter/randn
: create an iterator for generating pseudorandom numbers drawn from a standard normal distribution.@stdlib/random-streams/box-muller
: create a readable stream for generating pseudorandom numbers drawn from a standard normal distribution using the Box-Muller transform.@stdlib/random-streams/improved-ziggurat
: create a readable stream for generating pseudorandom numbers drawn from a standard normal distribution using the Improved Ziggurat algorithm.
This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.
For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.
See LICENSE.
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