kernel_density_estimation/kernel/
epanechnikov.rs

1//! Epanechnikov kernel function.
2
3use crate::float::{float, KDEFloat};
4use crate::kernel::Kernel;
5
6/// Epanechnikov kernel function.
7#[derive(Clone, Copy, Debug)]
8pub struct Epanechnikov;
9
10impl<F: KDEFloat> Kernel<F> for Epanechnikov {
11    fn pdf(&self, x: F) -> F {
12        let term = F::one() - x.powi(2);
13        if term > F::zero() {
14            float!(3.0 / 4.0) * term
15        } else {
16            F::zero()
17        }
18    }
19}
20
21#[cfg(test)]
22mod tests {
23    use super::Epanechnikov;
24    use crate::kernel::Kernel;
25    use approx::*;
26
27    #[test]
28    fn epanechnikov() {
29        let kernel = Epanechnikov;
30
31        let x = 0.0;
32        let res = kernel.pdf(x);
33        assert_relative_eq!(res, 0.75);
34
35        let x = -1.0;
36        let res = kernel.pdf(x);
37        assert_relative_eq!(res, 0.0);
38
39        let x = 1.0;
40        let res = kernel.pdf(x);
41        assert_relative_eq!(res, 0.0);
42    }
43}