kernel_density_estimation/kernel/
logistic.rs

1//! Logistic kernel function.
2
3use crate::float::{float, primitive, KDEFloat};
4use crate::kernel::Kernel;
5
6use std::f64::consts::E;
7
8/// Logistic kernel function.
9#[derive(Clone, Copy, Debug)]
10pub struct Logistic;
11
12impl<F: KDEFloat> Kernel<F> for Logistic {
13    fn pdf(&self, x: F) -> F {
14        let exp_neg_x = E.powf(primitive!(-x));
15        let exp_x = E.powf(primitive!(x));
16        float!(1.0 / (exp_neg_x + 2.0 + exp_x))
17    }
18}
19
20#[cfg(test)]
21mod tests {
22    use super::Logistic;
23    use crate::kernel::Kernel;
24    use approx::*;
25
26    #[test]
27    fn logistic() {
28        let kernel = Logistic;
29
30        let x = 0.0;
31        let res = kernel.pdf(x);
32        assert_relative_eq!(res, 0.25, epsilon = 1.0e-5);
33
34        let x = -1.0;
35        let res = kernel.pdf(x);
36        assert_relative_eq!(res, 0.19661, epsilon = 1.0e-5);
37
38        let x = 1.0;
39        let res = kernel.pdf(x);
40        assert_relative_eq!(res, 0.19661, epsilon = 1.0e-5);
41
42        let x = 0.5;
43        let res = kernel.pdf(x);
44        assert_relative_eq!(res, 0.23500, epsilon = 1.0e-5);
45    }
46}