feat: add C implementation for @stdlib/stats/base/dists/rayleigh/quan…

…tile

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---

@@ -147,6 +147,89 @@ for ( i = 0; i < 10; i++ ) {
 
 <!-- /.examples -->
 
+<!-- C interface documentation. -->
+
+* * *
+
+<section class="c">
+
+## C APIs
+
+<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->
+
+<section class="intro">
+
+</section>
+
+<!-- /.intro -->
+
+<!-- C usage documentation. -->
+
+<section class="usage">
+
+### Usage
+
+```c
+#include "stdlib/stats/base/dists/rayleigh/quantile.h"
+```
+
+#### stdlib_base_dists_rayleigh_quantile( p, sigma )
+
+Evaluates the quantile function for a Rayleigh distribution.
+
+```c
+double out = stdlib_base_dists_rayleigh_quantile( 0.8, 1.0 );
+// returns ~1.794
+```
+
+The function accepts the following arguments:
+
+- **p**: `[in] double` input value.
+- **sigma**: `[in] double` scale parameter.
+
+```c
+double stdlib_base_dists_rayleigh_quantile( const double p, const double sigma );
+```
+
+</section>
+<!-- /.usage -->
+<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+<section class="notes">
+</section>
+<!-- /.notes -->
+<!-- C API usage examples. -->
+<section class="examples">
+### Examples
+```c
+#include "stdlib/stats/base/dists/rayleigh/quantile.h"
+#include <stdlib.h>
+#include <stdio.h>
+static double random_uniform( const double min, const double max ) {
+double v = (double)rand() / ( (double)RAND_MAX + 1.0 );
+return min + ( v*(max-min) );
+}
+int main( void ) {
+double sigma;
+double p;
+double y;
+int i;
+for ( i = 0; i < 25; i++ ) {
+p = random_uniform( 0.0, 10.0 );
+sigma = random_uniform( 0.0, 10.0 );
+y = stdlib_base_dists_rayleigh_quantile( p, sigma );
+printf( "p: %lf, σ: %lf, f(x;σ): %lf\n", p, sigma, y );
+}
+}
+```
+
+</section>
+
+<!-- /.examples -->
+
+</section>
+
+<!-- /.c -->
+
 <!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->
 
 <section class="related">

@@ -21,6 +21,7 @@
 // MODULES //
 
 var bench = require( '@stdlib/bench' );
+var Float64Array = require( '@stdlib/array/float64' );
 var randu = require( '@stdlib/random/base/randu' );
 var isnan = require( '@stdlib/math/base/assert/is-nan' );
 var EPS = require( '@stdlib/constants/float64/eps' );
@@ -32,15 +33,22 @@ var quantile = require( './../lib' );
 
 bench( pkg, function benchmark( b ) {
 var sigma;
+var len;
 var p;
 var y;
 var i;
 
+len = 100;
+p = new Float64Array( len );
+sigma = new Float64Array( len );
+for ( i = 0; i < len; i++ ) {
+p[ i ] = randu();
+sigma[ i ] = ( randu() * 20.0 ) + EPS;
+}
+
 b.tic();
 for ( i = 0; i < b.iterations; i++ ) {
-p = randu();
-sigma = ( randu()*20.0 ) + EPS;
-y = quantile( p, sigma );
+y = quantile( p[ i % len ], sigma[ i % len ] );
 if ( isnan( y ) ) {
 b.fail( 'should not return NaN' );
 }

@@ -0,0 +1,71 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2018 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.
+*/
+
+'use strict';
+
+// MODULES //
+
+var resolve = require( 'path' ).resolve;
+var bench = require( '@stdlib/bench' );
+var Float64Array = require( '@stdlib/array/float64' );
+var tryRequire = require( '@stdlib/utils/try-require' );
+var randu = require( '@stdlib/random/base/randu' );
+var isnan = require( '@stdlib/math/base/assert/is-nan' );
+var EPS = require( '@stdlib/constants/float64/eps' );
+var pkg = require( './../package.json' ).name;
+
+
+// VARIABLES //
+
+var quantile = tryRequire( resolve( __dirname, './../lib/native.js' ) );
+var opts = {
+'skip': ( quantile instanceof Error )
+};
+
+
+// MAIN //
+
+bench( pkg, opts, function benchmark( b ) {
+var sigma;
+var len;
+var p;
+var y;
+var i;
+
+len = 100;
+p = new Float64Array( len );
+sigma = new Float64Array( len );
+for ( i = 0; i < len; i++ ) {
+p[ i ] = ( randu() * 100.0 ) - 100;
+sigma[ i ] = ( randu() * 20.0 ) + EPS;
+}
+
+b.tic();
+for ( i = 0; i < b.iterations; i++ ) {
+y = quantile( p[ i % len ], sigma[ i % len ] );
+if ( isnan( y ) ) {
+b.fail( 'should not return NaN' );
+}
+}
+b.toc();
+if ( isnan( y ) ) {
+b.fail( 'should not return NaN' );
+}
+b.pass( 'benchmark finished' );
+b.end();
+});