194 lines
4.1 KiB
Markdown
194 lines
4.1 KiB
Markdown
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<!--
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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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# Ramp Function
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> Evaluate the [ramp function][ramp-function].
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<section class="intro">
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The [ramp function][ramp-function] is defined as
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<!-- <equation class="equation" label="eq:ramp_function" align="center" raw="R(x) = \begin{cases} x & \textrm{if}\ x \geq 0 \\ 0 & \textrm{if}\ x \lt 0\end{cases}" alt="Ramp function."> -->
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<div class="equation" align="center" data-raw-text="R(x) = \begin{cases} x & \textrm{if}\ x \geq 0 \\ 0 & \textrm{if}\ x \lt 0\end{cases}" data-equation="eq:ramp_function">
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<img src="https://cdn.jsdelivr.net/gh/stdlib-js/stdlib@bb29798906e119fcb2af99e94b60407a270c9b32/lib/node_modules/@stdlib/math/base/special/ramp/docs/img/equation_ramp_function.svg" alt="Ramp function.">
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<br>
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</div>
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<!-- </equation> -->
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or, alternatively, in terms of the `max` function
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<!-- <equation class="equation" label="eq:ramp_function_alternative_defn" align="center" raw="R(x) = \operatorname{max}( x, 0 )" alt="Ramp function alternative definition."> -->
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<div class="equation" align="center" data-raw-text="R(x) = \operatorname{max}( x, 0 )" data-equation="eq:ramp_function_alternative_defn">
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<img src="https://cdn.jsdelivr.net/gh/stdlib-js/stdlib@bb29798906e119fcb2af99e94b60407a270c9b32/lib/node_modules/@stdlib/math/base/special/ramp/docs/img/equation_ramp_function_alternative_defn.svg" alt="Ramp function alternative definition.">
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<br>
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</div>
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<!-- </equation> -->
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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 ramp = require( '@stdlib/math/base/special/ramp' );
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```
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#### ramp( x )
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Evaluates the [ramp function][ramp-function].
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```javascript
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var v = ramp( 3.14 );
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// returns 3.14
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v = ramp( -3.14 );
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// returns 0.0
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v = ramp( 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 ramp = require( '@stdlib/math/base/special/ramp' );
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var x = linspace( -10.0, 10.0, 101 );
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var i;
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for ( i = 0; i < x.length; i++ ) {
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console.log( 'R(%d) = %d', x[ i ], ramp( x[ i ] ) );
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}
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```
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</section>
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<!-- /.examples -->
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<!-- C interface documentation. -->
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* * *
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<section class="c">
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## C APIs
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<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->
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<section class="intro">
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</section>
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<!-- /.intro -->
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<!-- C usage documentation. -->
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<section class="usage">
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### Usage
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```c
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#include "stdlib/math/base/special/ramp.h"
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```
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#### stdlib_base_ramp( x )
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Evaluates the ramp function.
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```c
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double y = stdlib_base_ramp( 3.0 );
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// returns 3.0
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```
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The function accepts the following arguments:
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- **x**: `[in] double` input value.
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```c
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double stdlib_base_ramp( const double x );
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```
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</section>
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<!-- /.usage -->
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<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="notes">
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</section>
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<!-- /.notes -->
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<!-- C API usage examples. -->
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<section class="examples">
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### Examples
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```c
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#include "stdlib/math/base/special/ramp.h"
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#include <stdio.h>
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int main() {
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double x[] = { 3.14, -3.14, 0.0, 0.0/0.0 };
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double y;
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int i;
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for ( i = 0; i < 4; i++ ) {
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y = stdlib_base_ramp( x[ i ] );
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printf( "R(%lf) = %lf\n", x[ i ], y );
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}
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}
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```
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</section>
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<!-- /.examples -->
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</section>
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<!-- /.c -->
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<section class="links">
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[ramp-function]: https://en.wikipedia.org/wiki/Ramp_function
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</section>
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<!-- /.links -->
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