kernel_density_estimation/kernel/
sigmoid.rs

1//! Sigmoid kernel function.
2
3use crate::float::{float, primitive, KDEFloat};
4use crate::kernel::Kernel;
5
6use std::f64::consts::{E, FRAC_2_PI};
7
8/// Sigmoid kernel function.
9#[derive(Clone, Copy, Debug)]
10pub struct Sigmoid;
11
12impl<F: KDEFloat> Kernel<F> for Sigmoid {
13    fn pdf(&self, x: F) -> F {
14        let numerator = float!(FRAC_2_PI);
15        let denominator = float!(E.powf(primitive!(x)) + E.powf(primitive!(-x)));
16        numerator / denominator
17    }
18}
19
20#[cfg(test)]
21mod tests {
22    use super::Sigmoid;
23    use crate::kernel::Kernel;
24    use approx::*;
25
26    #[test]
27    fn sigmoid() {
28        let kernel = Sigmoid;
29
30        let x = 0.0;
31        let res = kernel.pdf(x);
32        assert_relative_eq!(res, 0.31831, epsilon = 1.0e-5);
33
34        let x = -1.0;
35        let res = kernel.pdf(x);
36        assert_relative_eq!(res, 0.20628, epsilon = 1.0e-5);
37
38        let x = 1.0;
39        let res = kernel.pdf(x);
40        assert_relative_eq!(res, 0.20628, epsilon = 1.0e-5);
41
42        let x = 0.5;
43        let res = kernel.pdf(x);
44        assert_relative_eq!(res, 0.28228, epsilon = 1.0e-5);
45    }
46}
kernel_density_estimation/kernel/sigmoid.rs

kernel_density_estimation/kernel/
sigmoid.rs
