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<h1 class='fqn'><span class='in-band'>Struct <a href='../../index.html'>rand</a>::<wbr><a href='../index.html'>distributions</a>::<wbr><a href='index.html'>gamma</a>::<wbr><a class='struct' href=''>Gamma</a></span><span class='out-of-band'><span id='render-detail'>
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[<span class='inner'>−</span>]
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</span><a id='src-212' class='srclink' href='../../../src/rand/distributions/gamma.rs.html#53-55' title='goto source code'>[src]</a></span></h1>
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<pre class='rust struct'>pub struct Gamma {
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// some fields omitted
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}</pre><div class='docblock'><p>The Gamma distribution <code>Gamma(shape, scale)</code> distribution.</p>
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<p>The density function of this distribution is</p>
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<pre><code class="language-text">f(x) = x^(k - 1) * exp(-x / θ) / (Γ(k) * θ^k)
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</code></pre>
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<p>where <code>Γ</code> is the Gamma function, <code>k</code> is the shape and <code>θ</code> is the
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scale and both <code>k</code> and <code>θ</code> are strictly positive.</p>
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<p>The algorithm used is that described by Marsaglia & Tsang 2000[1],
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falling back to directly sampling from an Exponential for <code>shape == 1</code>, and using the boosting technique described in [1] for
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<code>shape < 1</code>.</p>
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<h1 id='example' class='section-header'><a href='#example'>Example</a></h1>
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<pre class='rust rust-example-rendered'>
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<span class='kw'>use</span> <span class='ident'>rand</span>::<span class='ident'>distributions</span>::{<span class='ident'>IndependentSample</span>, <span class='ident'>Gamma</span>};
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<span class='kw'>let</span> <span class='ident'>gamma</span> <span class='op'>=</span> <span class='ident'>Gamma</span>::<span class='ident'>new</span>(<span class='number'>2.0</span>, <span class='number'>5.0</span>);
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<span class='kw'>let</span> <span class='ident'>v</span> <span class='op'>=</span> <span class='ident'>gamma</span>.<span class='ident'>ind_sample</span>(<span class='kw-2'>&</span><span class='kw-2'>mut</span> <span class='ident'>rand</span>::<span class='ident'>thread_rng</span>());
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<span class='macro'>println</span><span class='macro'>!</span>(<span class='string'>"{} is from a Gamma(2, 5) distribution"</span>, <span class='ident'>v</span>);</pre>
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<p>[1]: George Marsaglia and Wai Wan Tsang. 2000. "A Simple Method
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for Generating Gamma Variables" <em>ACM Trans. Math. Softw.</em> 26, 3
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(September 2000),
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363-372. DOI:<a href="http://doi.acm.org/10.1145/358407.358414">10.1145/358407.358414</a></p>
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</div><h2 id='methods'>Methods</h2><h3 class='impl'><span class='in-band'><code>impl <a class='struct' href='../../../rand/distributions/gamma/struct.Gamma.html' title='rand::distributions::gamma::Gamma'>Gamma</a></code></span><span class='out-of-band'><div class='ghost'></div><a id='src-253' class='srclink' href='../../../src/rand/distributions/gamma.rs.html#95-111' title='goto source code'>[src]</a></span></h3>
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<div class='impl-items'><h4 id='method.new' class='method'><code>fn <a href='#method.new' class='fnname'>new</a>(shape: <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.f64.html'>f64</a>, scale: <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.f64.html'>f64</a>) -> <a class='struct' href='../../../rand/distributions/gamma/struct.Gamma.html' title='rand::distributions::gamma::Gamma'>Gamma</a></code></h4>
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<div class='docblock'><p>Construct an object representing the <code>Gamma(shape, scale)</code>
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distribution.</p>
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<p>Panics if <code>shape <= 0</code> or <code>scale <= 0</code>.</p>
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</div></div><h2 id='implementations'>Trait Implementations</h2><h3 class='impl'><span class='in-band'><code>impl <a class='trait' href='../../../rand/distributions/trait.Sample.html' title='rand::distributions::Sample'>Sample</a><<a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.f64.html'>f64</a>> for <a class='struct' href='../../../rand/distributions/gamma/struct.Gamma.html' title='rand::distributions::gamma::Gamma'>Gamma</a></code></span><span class='out-of-band'><div class='ghost'></div><a id='src-269' class='srclink' href='../../../src/rand/distributions/gamma.rs.html#133-135' title='goto source code'>[src]</a></span></h3>
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<div class='impl-items'><h4 id='method.sample' class='method'><code>fn <a href='../../../rand/distributions/trait.Sample.html#tymethod.sample' class='fnname'>sample</a><R: <a class='trait' href='../../../rand/trait.Rng.html' title='rand::Rng'>Rng</a>>(&mut self, rng: &mut R) -> <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.f64.html'>f64</a></code></h4>
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</div><h3 class='impl'><span class='in-band'><code>impl <a class='trait' href='../../../rand/distributions/trait.IndependentSample.html' title='rand::distributions::IndependentSample'>IndependentSample</a><<a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.f64.html'>f64</a>> for <a class='struct' href='../../../rand/distributions/gamma/struct.Gamma.html' title='rand::distributions::gamma::Gamma'>Gamma</a></code></span><span class='out-of-band'><div class='ghost'></div><a id='src-284' class='srclink' href='../../../src/rand/distributions/gamma.rs.html#143-151' title='goto source code'>[src]</a></span></h3>
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<div class='impl-items'><h4 id='method.ind_sample' class='method'><code>fn <a href='../../../rand/distributions/trait.IndependentSample.html#tymethod.ind_sample' class='fnname'>ind_sample</a><R: <a class='trait' href='../../../rand/trait.Rng.html' title='rand::Rng'>Rng</a>>(&self, rng: &mut R) -> <a class='primitive' href='https://doc.rust-lang.org/nightly/std/primitive.f64.html'>f64</a></code></h4>
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</div><h3 id='derived_implementations'>Derived Implementations </h3><h3 class='impl'><span class='in-band'><code>impl <a class='trait' href='https://doc.rust-lang.org/nightly/core/marker/trait.Copy.html' title='core::marker::Copy'>Copy</a> for <a class='struct' href='../../../rand/distributions/gamma/struct.Gamma.html' title='rand::distributions::gamma::Gamma'>Gamma</a></code></span><span class='out-of-band'><div class='ghost'></div><a id='src-214' class='srclink' href='../../../src/rand/distributions/gamma.rs.html#52' title='goto source code'>[src]</a></span></h3>
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<div class='impl-items'></div><h3 class='impl'><span class='in-band'><code>impl <a class='trait' href='https://doc.rust-lang.org/nightly/core/clone/trait.Clone.html' title='core::clone::Clone'>Clone</a> for <a class='struct' href='../../../rand/distributions/gamma/struct.Gamma.html' title='rand::distributions::gamma::Gamma'>Gamma</a></code></span><span class='out-of-band'><div class='ghost'></div><a id='src-215' class='srclink' href='../../../src/rand/distributions/gamma.rs.html#52' title='goto source code'>[src]</a></span></h3>
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<div class='impl-items'><h4 id='method.clone' class='method'><code>fn <a href='https://doc.rust-lang.org/nightly/core/clone/trait.Clone.html#tymethod.clone' class='fnname'>clone</a>(&self) -> <a class='struct' href='../../../rand/distributions/gamma/struct.Gamma.html' title='rand::distributions::gamma::Gamma'>Gamma</a></code></h4>
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<h4 id='method.clone_from' class='method'><code>fn <a href='https://doc.rust-lang.org/nightly/core/clone/trait.Clone.html#method.clone_from' class='fnname'>clone_from</a>(&mut self, source: &Self)</code><div class="since">1.0.0</div></h4>
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