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</pre><div class="example-wrap"><pre class="rust ">
<span class="comment">// Copyright 2018 Developers of the Rand project.</span>
<span class="comment">// Copyright 2013 The Rust Project Developers.</span>
<span class="comment">//</span>
<span class="comment">// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or</span>
<span class="comment">// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license</span>
<span class="comment">// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your</span>
<span class="comment">// option. This file may not be copied, modified, or distributed</span>
<span class="comment">// except according to those terms.</span>
<span class="doccomment">//! The dirichlet distribution.</span>
<span class="kw">use</span> <span class="ident">Rng</span>;
<span class="kw">use</span> <span class="ident">distributions</span>::<span class="ident">Distribution</span>;
<span class="kw">use</span> <span class="ident">distributions</span>::<span class="ident">gamma</span>::<span class="ident">Gamma</span>;
<span class="doccomment">/// The dirichelet distribution `Dirichlet(alpha)`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The Dirichlet distribution is a family of continuous multivariate</span>
<span class="doccomment">/// probability distributions parameterized by a vector alpha of positive reals.</span>
<span class="doccomment">/// It is a multivariate generalization of the beta distribution.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Example</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use rand::prelude::*;</span>
<span class="doccomment">/// use rand::distributions::Dirichlet;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let dirichlet = Dirichlet::new(vec![1.0, 2.0, 3.0]);</span>
<span class="doccomment">/// let samples = dirichlet.sample(&mut rand::thread_rng());</span>
<span class="doccomment">/// println!("{:?} is from a Dirichlet([1.0, 2.0, 3.0]) distribution", samples);</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">Dirichlet</span> {
<span class="doccomment">/// Concentration parameters (alpha)</span>
<span class="ident">alpha</span>: <span class="ident">Vec</span><span class="op"><</span><span class="ident">f64</span><span class="op">></span>,
}
<span class="kw">impl</span> <span class="ident">Dirichlet</span> {
<span class="doccomment">/// Construct a new `Dirichlet` with the given alpha parameter `alpha`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Panics</span>
<span class="doccomment">/// - if `alpha.len() < 2`</span>
<span class="doccomment">///</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span><span class="op"><</span><span class="ident">V</span>: <span class="ident">Into</span><span class="op"><</span><span class="ident">Vec</span><span class="op"><</span><span class="ident">f64</span><span class="op">></span><span class="op">></span><span class="op">></span>(<span class="ident">alpha</span>: <span class="ident">V</span>) <span class="op">-</span><span class="op">></span> <span class="ident">Dirichlet</span> {
<span class="kw">let</span> <span class="ident">a</span> <span class="op">=</span> <span class="ident">alpha</span>.<span class="ident">into</span>();
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">a</span>.<span class="ident">len</span>() <span class="op">></span> <span class="number">1</span>);
<span class="kw">for</span> <span class="ident">i</span> <span class="kw">in</span> <span class="number">0</span>..<span class="ident">a</span>.<span class="ident">len</span>() {
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">a</span>[<span class="ident">i</span>] <span class="op">></span> <span class="number">0.0</span>);
}
<span class="ident">Dirichlet</span> { <span class="ident">alpha</span>: <span class="ident">a</span> }
}
<span class="doccomment">/// Construct a new `Dirichlet` with the given shape parameter `alpha` and `size`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Panics</span>
<span class="doccomment">/// - if `alpha <= 0.0`</span>
<span class="doccomment">/// - if `size < 2`</span>
<span class="doccomment">///</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new_with_param</span>(<span class="ident">alpha</span>: <span class="ident">f64</span>, <span class="ident">size</span>: <span class="ident">usize</span>) <span class="op">-</span><span class="op">></span> <span class="ident">Dirichlet</span> {
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">alpha</span> <span class="op">></span> <span class="number">0.0</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">size</span> <span class="op">></span> <span class="number">1</span>);
<span class="ident">Dirichlet</span> {
<span class="ident">alpha</span>: <span class="macro">vec</span><span class="macro">!</span>[<span class="ident">alpha</span>; <span class="ident">size</span>],
}
}
}
<span class="kw">impl</span> <span class="ident">Distribution</span><span class="op"><</span><span class="ident">Vec</span><span class="op"><</span><span class="ident">f64</span><span class="op">></span><span class="op">></span> <span class="kw">for</span> <span class="ident">Dirichlet</span> {
<span class="kw">fn</span> <span class="ident">sample</span><span class="op"><</span><span class="ident">R</span>: <span class="ident">Rng</span> <span class="op">+</span> <span class="question-mark">?</span><span class="ident">Sized</span><span class="op">></span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">rng</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">R</span>) <span class="op">-</span><span class="op">></span> <span class="ident">Vec</span><span class="op"><</span><span class="ident">f64</span><span class="op">></span> {
<span class="kw">let</span> <span class="ident">n</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">alpha</span>.<span class="ident">len</span>();
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">samples</span> <span class="op">=</span> <span class="macro">vec</span><span class="macro">!</span>[<span class="number">0.0f64</span>; <span class="ident">n</span>];
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">sum</span> <span class="op">=</span> <span class="number">0.0f64</span>;
<span class="kw">for</span> <span class="ident">i</span> <span class="kw">in</span> <span class="number">0</span>..<span class="ident">n</span> {
<span class="kw">let</span> <span class="ident">g</span> <span class="op">=</span> <span class="ident">Gamma</span>::<span class="ident">new</span>(<span class="self">self</span>.<span class="ident">alpha</span>[<span class="ident">i</span>], <span class="number">1.0</span>);
<span class="ident">samples</span>[<span class="ident">i</span>] <span class="op">=</span> <span class="ident">g</span>.<span class="ident">sample</span>(<span class="ident">rng</span>);
<span class="ident">sum</span> <span class="op">+</span><span class="op">=</span> <span class="ident">samples</span>[<span class="ident">i</span>];
}
<span class="kw">let</span> <span class="ident">invacc</span> <span class="op">=</span> <span class="number">1.0</span> <span class="op">/</span> <span class="ident">sum</span>;
<span class="kw">for</span> <span class="ident">i</span> <span class="kw">in</span> <span class="number">0</span>..<span class="ident">n</span> {
<span class="ident">samples</span>[<span class="ident">i</span>] <span class="kw-2">*</span><span class="op">=</span> <span class="ident">invacc</span>;
}
<span class="ident">samples</span>
}
}
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">test</span>)]</span>
<span class="kw">mod</span> <span class="ident">test</span> {
<span class="kw">use</span> <span class="kw">super</span>::<span class="ident">Dirichlet</span>;
<span class="kw">use</span> <span class="ident">distributions</span>::<span class="ident">Distribution</span>;
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_dirichlet</span>() {
<span class="kw">let</span> <span class="ident">d</span> <span class="op">=</span> <span class="ident">Dirichlet</span>::<span class="ident">new</span>(<span class="macro">vec</span><span class="macro">!</span>[<span class="number">1.0</span>, <span class="number">2.0</span>, <span class="number">3.0</span>]);
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">rng</span> <span class="op">=</span> ::<span class="ident">test</span>::<span class="ident">rng</span>(<span class="number">221</span>);
<span class="kw">let</span> <span class="ident">samples</span> <span class="op">=</span> <span class="ident">d</span>.<span class="ident">sample</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">rng</span>);
<span class="kw">let</span> <span class="kw">_</span>: <span class="ident">Vec</span><span class="op"><</span><span class="ident">f64</span><span class="op">></span> <span class="op">=</span> <span class="ident">samples</span>
.<span class="ident">into_iter</span>()
.<span class="ident">map</span>(<span class="op">|</span><span class="ident">x</span><span class="op">|</span> {
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">x</span> <span class="op">></span> <span class="number">0.0</span>);
<span class="ident">x</span>
})
.<span class="ident">collect</span>();
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">test_dirichlet_with_param</span>() {
<span class="kw">let</span> <span class="ident">alpha</span> <span class="op">=</span> <span class="number">0.5f64</span>;
<span class="kw">let</span> <span class="ident">size</span> <span class="op">=</span> <span class="number">2</span>;
<span class="kw">let</span> <span class="ident">d</span> <span class="op">=</span> <span class="ident">Dirichlet</span>::<span class="ident">new_with_param</span>(<span class="ident">alpha</span>, <span class="ident">size</span>);
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">rng</span> <span class="op">=</span> ::<span class="ident">test</span>::<span class="ident">rng</span>(<span class="number">221</span>);
<span class="kw">let</span> <span class="ident">samples</span> <span class="op">=</span> <span class="ident">d</span>.<span class="ident">sample</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">rng</span>);
<span class="kw">let</span> <span class="kw">_</span>: <span class="ident">Vec</span><span class="op"><</span><span class="ident">f64</span><span class="op">></span> <span class="op">=</span> <span class="ident">samples</span>
.<span class="ident">into_iter</span>()
.<span class="ident">map</span>(<span class="op">|</span><span class="ident">x</span><span class="op">|</span> {
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">x</span> <span class="op">></span> <span class="number">0.0</span>);
<span class="ident">x</span>
})
.<span class="ident">collect</span>();
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="attribute">#[<span class="ident">should_panic</span>]</span>
<span class="kw">fn</span> <span class="ident">test_dirichlet_invalid_length</span>() {
<span class="ident">Dirichlet</span>::<span class="ident">new_with_param</span>(<span class="number">0.5f64</span>, <span class="number">1</span>);
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="attribute">#[<span class="ident">should_panic</span>]</span>
<span class="kw">fn</span> <span class="ident">test_dirichlet_invalid_alpha</span>() {
<span class="ident">Dirichlet</span>::<span class="ident">new_with_param</span>(<span class="number">0.0f64</span>, <span class="number">2</span>);
}
}
</pre></div>
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