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| </pre><pre class="rust"><code><span class="comment">// Copyright 2018 Developers of the Rand project. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // https://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| </span><span class="doccomment">//! The triangular distribution. |
| |
| </span><span class="kw">use </span>num_traits::Float; |
| <span class="kw">use crate</span>::{Distribution, Standard}; |
| <span class="kw">use </span>rand::Rng; |
| <span class="kw">use </span>core::fmt; |
| |
| <span class="doccomment">/// The triangular distribution. |
| /// |
| /// A continuous probability distribution parameterised by a range, and a mode |
| /// (most likely value) within that range. |
| /// |
| /// The probability density function is triangular. For a similar distribution |
| /// with a smooth PDF, see the [`Pert`] distribution. |
| /// |
| /// # Example |
| /// |
| /// ```rust |
| /// use rand_distr::{Triangular, Distribution}; |
| /// |
| /// let d = Triangular::new(0., 5., 2.5).unwrap(); |
| /// let v = d.sample(&mut rand::thread_rng()); |
| /// println!("{} is from a triangular distribution", v); |
| /// ``` |
| /// |
| /// [`Pert`]: crate::Pert |
| </span><span class="attribute">#[derive(Clone, Copy, Debug)] |
| #[cfg_attr(feature = <span class="string">"serde1"</span>, derive(serde::Serialize, serde::Deserialize))] |
| </span><span class="kw">pub struct </span>Triangular<F> |
| <span class="kw">where </span>F: Float, Standard: Distribution<F> |
| { |
| min: F, |
| max: F, |
| mode: F, |
| } |
| |
| <span class="doccomment">/// Error type returned from [`Triangular::new`]. |
| </span><span class="attribute">#[derive(Clone, Copy, Debug, PartialEq, Eq)] |
| </span><span class="kw">pub enum </span>TriangularError { |
| <span class="doccomment">/// `max < min` or `min` or `max` is NaN. |
| </span>RangeTooSmall, |
| <span class="doccomment">/// `mode < min` or `mode > max` or `mode` is NaN. |
| </span>ModeRange, |
| } |
| |
| <span class="kw">impl </span>fmt::Display <span class="kw">for </span>TriangularError { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, f: <span class="kw-2">&mut </span>fmt::Formatter<<span class="lifetime">'_</span>>) -> fmt::Result { |
| f.write_str(<span class="kw">match </span><span class="self">self </span>{ |
| TriangularError::RangeTooSmall => { |
| <span class="string">"requirement min <= max is not met in triangular distribution" |
| </span>} |
| TriangularError::ModeRange => <span class="string">"mode is outside [min, max] in triangular distribution"</span>, |
| }) |
| } |
| } |
| |
| <span class="attribute">#[cfg(feature = <span class="string">"std"</span>)] |
| #[cfg_attr(doc_cfg, doc(cfg(feature = <span class="string">"std"</span>)))] |
| </span><span class="kw">impl </span>std::error::Error <span class="kw">for </span>TriangularError {} |
| |
| <span class="kw">impl</span><F> Triangular<F> |
| <span class="kw">where </span>F: Float, Standard: Distribution<F> |
| { |
| <span class="doccomment">/// Set up the Triangular distribution with defined `min`, `max` and `mode`. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub fn </span>new(min: F, max: F, mode: F) -> <span class="prelude-ty">Result</span><Triangular<F>, TriangularError> { |
| <span class="kw">if </span>!(max >= min) { |
| <span class="kw">return </span><span class="prelude-val">Err</span>(TriangularError::RangeTooSmall); |
| } |
| <span class="kw">if </span>!(mode >= min && max >= mode) { |
| <span class="kw">return </span><span class="prelude-val">Err</span>(TriangularError::ModeRange); |
| } |
| <span class="prelude-val">Ok</span>(Triangular { min, max, mode }) |
| } |
| } |
| |
| <span class="kw">impl</span><F> Distribution<F> <span class="kw">for </span>Triangular<F> |
| <span class="kw">where </span>F: Float, Standard: Distribution<F> |
| { |
| <span class="attribute">#[inline] |
| </span><span class="kw">fn </span>sample<R: Rng + <span class="question-mark">?</span>Sized>(<span class="kw-2">&</span><span class="self">self</span>, rng: <span class="kw-2">&mut </span>R) -> F { |
| <span class="kw">let </span>f: F = rng.sample(Standard); |
| <span class="kw">let </span>diff_mode_min = <span class="self">self</span>.mode - <span class="self">self</span>.min; |
| <span class="kw">let </span>range = <span class="self">self</span>.max - <span class="self">self</span>.min; |
| <span class="kw">let </span>f_range = f * range; |
| <span class="kw">if </span>f_range < diff_mode_min { |
| <span class="self">self</span>.min + (f_range * diff_mode_min).sqrt() |
| } <span class="kw">else </span>{ |
| <span class="self">self</span>.max - ((range - f_range) * (<span class="self">self</span>.max - <span class="self">self</span>.mode)).sqrt() |
| } |
| } |
| } |
| |
| <span class="attribute">#[cfg(test)] |
| </span><span class="kw">mod </span>test { |
| <span class="kw">use super</span>::<span class="kw-2">*</span>; |
| <span class="kw">use </span>rand::{rngs::mock, Rng}; |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>test_triangular() { |
| <span class="kw">let </span><span class="kw-2">mut </span>half_rng = mock::StepRng::new(<span class="number">0x8000_0000_0000_0000</span>, <span class="number">0</span>); |
| <span class="macro">assert_eq!</span>(half_rng.gen::<f64>(), <span class="number">0.5</span>); |
| <span class="kw">for </span><span class="kw-2">&</span>(min, max, mode, median) <span class="kw">in </span><span class="kw-2">&</span>[ |
| (-<span class="number">1.</span>, <span class="number">1.</span>, <span class="number">0.</span>, <span class="number">0.</span>), |
| (<span class="number">1.</span>, <span class="number">2.</span>, <span class="number">1.</span>, <span class="number">2. </span>- <span class="number">0.5f64</span>.sqrt()), |
| (<span class="number">5.</span>, <span class="number">25.</span>, <span class="number">25.</span>, <span class="number">5. </span>+ <span class="number">200f64</span>.sqrt()), |
| (<span class="number">1e-5</span>, <span class="number">1e5</span>, <span class="number">1e-3</span>, <span class="number">1e5 </span>- <span class="number">4999999949.5f64</span>.sqrt()), |
| (<span class="number">0.</span>, <span class="number">1.</span>, <span class="number">0.9</span>, <span class="number">0.45f64</span>.sqrt()), |
| (-<span class="number">4.</span>, -<span class="number">0.5</span>, -<span class="number">2.</span>, -<span class="number">4.0 </span>+ <span class="number">3.5f64</span>.sqrt()), |
| ] { |
| <span class="attribute">#[cfg(feature = <span class="string">"std"</span>)] |
| </span><span class="macro">std::println!</span>(<span class="string">"{} {} {} {}"</span>, min, max, mode, median); |
| <span class="kw">let </span>distr = Triangular::new(min, max, mode).unwrap(); |
| <span class="comment">// Test correct value at median: |
| </span><span class="macro">assert_eq!</span>(distr.sample(<span class="kw-2">&mut </span>half_rng), median); |
| } |
| |
| <span class="kw">for </span><span class="kw-2">&</span>(min, max, mode) <span class="kw">in </span><span class="kw-2">&</span>[ |
| (-<span class="number">1.</span>, <span class="number">1.</span>, <span class="number">2.</span>), |
| (-<span class="number">1.</span>, <span class="number">1.</span>, -<span class="number">2.</span>), |
| (<span class="number">2.</span>, <span class="number">1.</span>, <span class="number">1.</span>), |
| ] { |
| <span class="macro">assert!</span>(Triangular::new(min, max, mode).is_err()); |
| } |
| } |
| } |
| </code></pre></div> |
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