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# npm

## @stdlib/simulate-iter-periodic-sinc

0.0.6 • Public • Published

# iterPeriodicSinc

Create an iterator which generates a periodic sinc waveform.

The periodic sinc function, also known as the Dirichlet function, is defined as

where `N` is the function order and `A` is the peak amplitude. For odd `N`, the waveform has a period of `2π`, and, for even `N`, the waveform has a period of `4π`.

To express the periodic sinc function as a function of a discrete iteration number `t` and the waveform period `τ`, for odd `N`, let

and, for even `N`, let

where `τ` is the period (i.e., the number of iterations until a waveform repeats) and `φ` is the phase (iteration) offset. For odd `N`, we can thus substitute and express the periodic sinc function as

For even `N`, we can express the periodic sinc function similarly.

Note that the periodic sinc can be equivalently expressed as a function of the sinc function

## Installation

`npm install @stdlib/simulate-iter-periodic-sinc`

## Usage

`var iterPeriodicSinc = require( '@stdlib/simulate-iter-periodic-sinc' );`

#### iterPeriodicSinc( n[, options] )

Returns an iterator which generates a periodic sinc waveform of order `n`.

```var it = iterPeriodicSinc( 7 );
// returns <Object>

var v = it.next().value;
// returns <number>

v = it.next().value;
// returns <number>

v = it.next().value;
// returns <number>

// ...```

The returned iterator protocol-compliant object has the following properties:

• next: function which returns an iterator protocol-compliant object containing the next iterated value (if one exists) assigned to a `value` property and a `done` property having a `boolean` value indicating whether the iterator is finished.
• return: function which closes an iterator and returns a single (optional) argument in an iterator protocol-compliant object.

The function supports the following `options`:

• period: period (i.e., the number of iterations before a waveform repeats). Default: `100`.
• amplitude: peak amplitude. Default: `1.0`.
• offset: phase offset (in units of iterations; zero-based). A negative offset translates a waveform to the left. A positive offset translates a waveform to the right. Default: `0`.
• iter: number of iterations. Default: `1e308`.

By default, the function returns an iterator which generates a waveform that repeats every `100` iterations. To specify an alternative period, set the `period` option.

```var opts = {
'period': 1000
};

var it = iterPeriodicSinc( 7, opts );
// returns <Object>

var v = it.next().value;
// returns <number>

v = it.next().value;
// returns <number>

// ...```

To adjust at what point the iterator begins in the waveform cycle, set the phase `offset` option. For example, to translate the waveform to the left,

```var opts = {
'period': 100,
'offset': -1
};

var it = iterPeriodicSinc( 7, opts );
// returns <Object>

var v = it.next().value;
// returns <number>

v = it.next().value;
// returns <number>

// ...```

To translate the waveform to the right,

```var opts = {
'period': 100,
'offset': 1
};

var it = iterPeriodicSinc( 7, opts );
// returns <Object>

var v = it.next().value;
// returns <number>

v = it.next().value;
// returns <number>

// ...```

By default, the function returns an infinite iterator (i.e., an iterator which never ends). To limit the number of iterations, set the `iter` option.

```var opts = {
'iter': 2
};
var it = iterPeriodicSinc( 7, opts );
// returns <Object>

var v = it.next().value;
// returns <number>

v = it.next().value;
// returns <number>

var bool = it.next().done;
// returns true```

## Notes

• If an environment supports `Symbol.iterator`, the returned iterator is iterable.

## Examples

```var iterPeriodicSinc = require( '@stdlib/simulate-iter-periodic-sinc' );

// Create an iterator:
var opts = {
'period': 100,
'amplitude': 10.0,
'offset': -50,
'iter': 100
};
var it = iterPeriodicSinc( 7, opts );

// Perform manual iteration...
var v;
while ( true ) {
v = it.next();
if ( v.done ) {
break;
}
console.log( v.value );
}```

## Notice

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.

### Install

`npm i @stdlib/simulate-iter-periodic-sinc`

stdlib.io

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