@stdlib/simulate-iter-awun
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Create an iterator which introduces additive white uniform noise.
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JavaScript
/**
* @license Apache-2.0
*
* Copyright (c) 2019 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
;
// MODULES //
var setReadOnly = require( '@stdlib/utils-define-nonenumerable-read-only-property' );
var setReadOnlyAccessor = require( '@stdlib/utils-define-nonenumerable-read-only-accessor' );
var setReadWriteAccessor = require( '@stdlib/utils-define-nonenumerable-read-write-accessor' );
var isIteratorLike = require( '@stdlib/assert-is-iterator-like' );
var isPositiveNumber = require( '@stdlib/assert-is-positive-number' ).isPrimitive;
var isPlainObject = require( '@stdlib/assert-is-plain-object' );
var isFunction = require( '@stdlib/assert-is-function' );
var isBoolean = require( '@stdlib/assert-is-boolean' ).isPrimitive;
var isUint32Array = require( '@stdlib/assert-is-uint32array' );
var hasOwnProp = require( '@stdlib/assert-has-own-property' );
var noop = require( '@stdlib/utils-noop' );
var constantFunction = require( '@stdlib/utils-constant-function' );
var format = require( '@stdlib/string-format' );
var iteratorSymbol = require( '@stdlib/symbol-iterator' );
var randu = require( '@stdlib/random-base-uniform' ).factory;
var SQRT_THREE = require( '@stdlib/constants-float64-sqrt-three' );
var defaults = require( './defaults.js' );
// MAIN //
/**
* Returns an iterator which introduces additive white uniform noise with standard deviation `sigma`.
*
* ## Method
*
* - The variance of a uniform distribution is given by
*
* ```tex
* \operatorname{Var} = \frac{(b-a)^2}{12}
* ```
*
* where \\( a \\) is the minimum support and \\( b \\) is the maximum support.
*
* - Accordingly, to generate uniform noise having zero mean and a desired standard deviation, we let \\( a = -b \\) and solve for \\( b \\).
*
* ```tex
* \begin{align*}
* \sigma &= \frac{b-a}{\sqrt{12}} \\
* \sigma \sqrt{12} &= b - a \\
* 2 \sigma \sqrt{3} &= b - (-b) \\
* 2 \sigma \sqrt{3} &= 2b \\
* b &= \sigma \sqrt{3}
* \end{align*}
* ```
*
* where \\( \sigma \\) is the standard deviation.
*
* - Thus, to generate uniform noise having zero mean and a desired standard deviation, we sample from \\( \operatorname{unif}(-sigma\sqrt{3}, sigma\sqrt{3}) \\).
*
* @param {Iterator} iterator - input iterator
* @param {PositiveNumber} sigma - standard deviation of the noise
* @param {Options} [options] - function options
* @param {PRNG} [options.prng] - pseudorandom number generator which generates uniformly distributed pseudorandom numbers on the interval `[0,1)`
* @param {PRNGSeedMT19937} [options.seed] - pseudorandom number generator seed
* @param {PRNGStateMT19937} [options.state] - pseudorandom number generator state
* @param {boolean} [options.copy=true] - boolean indicating whether to copy a provided pseudorandom number generator state
* @throws {TypeError} first argument must be an iterator
* @throws {TypeError} second argument must be a positive number
* @throws {TypeError} third argument must be an object
* @throws {TypeError} must provide valid options
* @throws {Error} must provide a valid state
* @returns {Iterator} iterator
*
* @example
* var iterSineWave = require( '@stdlib/simulate-iter-sine-wave' );
*
* var sine = iterSineWave({
* 'iter': 100
* });
*
* var it = iterawun( sine, 0.5 );
*
* var v = it.next().value;
* // returns <number>
*
* v = it.next().value;
* // returns <number>
*
* v = it.next().value;
* // returns <number>
*
* // ...
*/
function iterawun( iterator, sigma, options ) {
var runif;
var opts;
var iter;
var FLG;
var a;
if ( !isIteratorLike( iterator ) ) {
throw new TypeError( format( 'invalid argument. First argument must be an iterator. Value: `%s`.', iterator ) );
}
if ( !isPositiveNumber( sigma ) ) {
throw new TypeError( format( 'invalid argument. Second argument must be a positive number. Value: `%s`.', sigma ) );
}
opts = defaults();
if ( arguments.length > 2 ) {
if ( !isPlainObject( options ) ) {
throw new TypeError( format( 'invalid argument. Third argument must be an object. Value: `%s`.', options ) );
}
if ( hasOwnProp( options, 'copy' ) ) {
opts.copy = options.copy;
if ( !isBoolean( options.copy ) ) {
throw new TypeError( format( 'invalid option. `%s` option must be a boolean. Option: `%s`.', 'copy', options.copy ) );
}
}
if ( hasOwnProp( options, 'prng' ) ) {
if ( !isFunction( options.prng ) ) {
throw new TypeError( format( 'invalid option. `%s` option must be a pseudorandom number generator function. Option: `%s`.', 'prng', options.prng ) );
}
opts.prng = options.prng;
}
// If provided a PRNG, ignore the `state` option, as we don't support getting or setting PRNG state.
else if ( hasOwnProp( options, 'state' ) ) {
opts.state = options.state;
if ( !isUint32Array( options.state ) ) {
throw new TypeError( format( 'invalid option. `%s` option must be a Uint32Array. Option: `%s`.', 'state', options.state ) );
}
}
// If provided a PRNG, ignore the `seed` option, as a `seed`, by itself, is insufficient to guarantee reproducibility. If provided a state, ignore the `seed` option, as a PRNG state should contain seed information.
else if ( hasOwnProp( options, 'seed' ) ) {
opts.seed = options.seed;
if ( options.seed === void 0 ) {
throw new TypeError( format( 'invalid option. `%s` option must be either a positive integer less than or equal to the maximum unsigned 32-bit integer or an array-like object containing integer values less than or equal to the maximum unsigned 32-bit integer. Option: `%s`.', 'seed', options.seed ) );
}
}
}
a = sigma * SQRT_THREE;
runif = randu( -a, a, opts );
// Create an iterator protocol-compliant object:
iter = {};
setReadOnly( iter, 'next', next );
setReadOnly( iter, 'return', end );
// If an environment supports `Symbol.iterator` and the provided iterator is iterable, make the iterator iterable:
if ( iteratorSymbol && isFunction( iterator[ iteratorSymbol ] ) ) {
setReadOnly( iter, iteratorSymbol, factory );
}
// If we are provided an "external" PRNG, we don't support getting or setting PRNG state, as we'd need to check for compatible state value types, etc, entailing considerable complexity.
if ( options && options.prng ) {
setReadOnly( iter, 'seed', null );
setReadOnly( iter, 'seedLength', null );
setReadWriteAccessor( iter, 'state', constantFunction( null ), noop );
setReadOnly( iter, 'stateLength', null );
setReadOnly( iter, 'byteLength', null );
setReadOnly( iter, 'PRNG', options.prng );
} else {
setReadOnlyAccessor( iter, 'seed', getSeed );
setReadOnlyAccessor( iter, 'seedLength', getSeedLength );
setReadWriteAccessor( iter, 'state', getState, setState );
setReadOnlyAccessor( iter, 'stateLength', getStateLength );
setReadOnlyAccessor( iter, 'byteLength', getStateSize );
setReadOnly( iter, 'PRNG', runif.PRNG );
}
return iter;
/**
* Returns the PRNG seed.
*
* @private
* @returns {PRNGSeedMT19937} seed
*/
function getSeed() {
return runif.seed;
}
/**
* Returns the PRNG seed length.
*
* @private
* @returns {PositiveInteger} seed length
*/
function getSeedLength() {
return runif.seedLength;
}
/**
* Returns the PRNG state length.
*
* @private
* @returns {PositiveInteger} state length
*/
function getStateLength() {
return runif.stateLength;
}
/**
* Returns the PRNG state size (in bytes).
*
* @private
* @returns {PositiveInteger} state size (in bytes)
*/
function getStateSize() {
return runif.byteLength;
}
/**
* Returns the current PRNG state.
*
* @private
* @returns {PRNGStateMT19937} current state
*/
function getState() {
return runif.state;
}
/**
* Sets the PRNG state.
*
* @private
* @param {PRNGStateMT19937} s - generator state
* @throws {Error} must provide a valid state
*/
function setState( s ) {
runif.state = s;
}
/**
* Returns an iterator protocol-compliant object containing the next iterated value.
*
* @private
* @returns {Object} iterator protocol-compliant object
*/
function next() {
var v;
if ( FLG ) {
return {
'done': true
};
}
v = iterator.next();
if ( v.done ) {
FLG = true;
return v;
}
if ( typeof v.value === 'number' ) {
v = v.value + runif();
} else {
v = NaN;
}
return {
'value': v,
'done': false
};
}
/**
* Finishes an iterator.
*
* @private
* @param {*} [value] - value to return
* @returns {Object} iterator protocol-compliant object
*/
function end( value ) {
FLG = true;
if ( arguments.length ) {
return {
'value': value,
'done': true
};
}
return {
'done': true
};
}
/**
* Returns a new iterator.
*
* @private
* @returns {Iterator} iterator
*/
function factory() {
return iterawun( iterator[ iteratorSymbol ](), sigma, opts );
}
}
// EXPORTS //
module.exports = iterawun;