103 lines
2.3 KiB
Markdown
103 lines
2.3 KiB
Markdown
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@license Apache-2.0
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Copyright (c) 2018 The Stdlib Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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# sinc
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> Compute the [cardinal sine][sinc] of a number.
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<section class="intro">
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The normalized [cardinal sine][sinc] function is defined as
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<!-- <equation class="equation" label="eq:sinc_function" align="center" raw="\operatorname{sinc}(x) := \begin{cases} \frac {\sin(\pi x)}{\pi x} & \textrm{if}\ x \neq 0 \\ 1 & \textrm{if}\ x = 0 \end{cases}" alt="Sinc function"> -->
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<div class="equation" align="center" data-raw-text="\operatorname{sinc}(x) := \begin{cases} \frac {\sin(\pi x)}{\pi x} & \textrm{if}\ x \neq 0 \\ 1 & \textrm{if}\ x = 0 \end{cases}" data-equation="eq:sinc_function">
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<img src="https://cdn.jsdelivr.net/gh/stdlib-js/stdlib@bb29798906e119fcb2af99e94b60407a270c9b32/lib/node_modules/@stdlib/math/base/special/sinc/docs/img/equation_sinc_function.svg" alt="Sinc function">
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<br>
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</div>
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<!-- </equation> -->
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for any real number `x`.
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</section>
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<!-- /.intro -->
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<section class="usage">
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## Usage
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```javascript
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var sinc = require( '@stdlib/math/base/special/sinc' );
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```
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#### sinc( x )
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Computes the normalized [cardinal sine][sinc] of a `number`.
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```javascript
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var v = sinc( 0.5 );
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// returns ~0.637
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v = sinc( -1.2 );
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// returns ~-0.156
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v = sinc( 0.0 );
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// returns 1.0
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v = sinc( NaN );
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// returns NaN
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```
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</section>
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<!-- /.usage -->
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<section class="examples">
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## Examples
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<!-- eslint no-undef: "error" -->
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```javascript
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var linspace = require( '@stdlib/array/linspace' );
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var sinc = require( '@stdlib/math/base/special/sinc' );
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var x = linspace( -5.0, 5.0, 100 );
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var i;
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for ( i = 0; i < x.length; i++ ) {
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console.log( sinc( x[ i ] ) );
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}
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```
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</section>
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<!-- /.examples -->
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<section class="links">
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[sinc]: https://en.wikipedia.org/wiki/Sinc_function
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</section>
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<!-- /.links -->
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