vendor/rand-0.7.3/src/distributions/weibull.rs

   1 // Copyright 2018 Developers of the Rand project.
   2 //
   3 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   4 // https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   5 // <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
   6 // option. This file may not be copied, modified, or distributed
   7 // except according to those terms.
   8
   9 //! The Weibull distribution.
  10 #![allow(deprecated)]
  11
  12 use crate::distributions::{Distribution, OpenClosed01};
  13 use crate::Rng;
  14
  15 /// Samples floating-point numbers according to the Weibull distribution
  16 #[deprecated(since = "0.7.0", note = "moved to rand_distr crate")]
  17 #[derive(Clone, Copy, Debug)]
  18 pub struct Weibull {
  19     inv_shape: f64,
  20     scale: f64,
  21 }
  22
  23 impl Weibull {
  24     /// Construct a new `Weibull` distribution with given `scale` and `shape`.
  25     ///
  26     /// # Panics
  27     ///
  28     /// `scale` and `shape` have to be non-zero and positive.
  29     pub fn new(scale: f64, shape: f64) -> Weibull {
  30         assert!((scale > 0.) & (shape > 0.));
  31         Weibull {
  32             inv_shape: 1. / shape,
  33             scale,
  34         }
  35     }
  36 }
  37
  38 impl Distribution<f64> for Weibull {
  39     fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> f64 {
  40         let x: f64 = rng.sample(OpenClosed01);
  41         self.scale * (-x.ln()).powf(self.inv_shape)
  42     }
  43 }
  44
  45 #[cfg(test)]
  46 mod tests {
  47     use super::Weibull;
  48     use crate::distributions::Distribution;
  49
  50     #[test]
  51     #[should_panic]
  52     fn invalid() {
  53         Weibull::new(0., 0.);
  54     }
  55
  56     #[test]
  57     fn sample() {
  58         let scale = 1.0;
  59         let shape = 2.0;
  60         let d = Weibull::new(scale, shape);
  61         let mut rng = crate::test::rng(1);
  62         for _ in 0..1000 {
  63             let r = d.sample(&mut rng);
  64             assert!(r >= 0.);
  65         }
  66     }
  67 }