cfbd45bfc0
* Improve features * Add wasm32-wasi as a target * Update .github/workflows/ci.yml Co-authored-by: morenol <22335041+morenol@users.noreply.github.com>
101 lines
2.9 KiB
Rust
101 lines
2.9 KiB
Rust
//! # Minkowski Distance
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//!
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//! The Minkowski distance of order _p_ (where _p_ is an integer) is a metric in a normed vector space which can be considered as a generalization of both the Euclidean distance and the Manhattan distance.
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//! The Manhattan distance between two points \\(x \in ℝ^n \\) and \\( y \in ℝ^n \\) in n-dimensional space is defined as:
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//!
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//! \\[ d(x, y) = \left(\sum_{i=0}^n \lvert x_i - y_i \rvert^p\right)^{1/p} \\]
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//!
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//! Example:
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//!
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//! ```
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//! use smartcore::metrics::distance::Distance;
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//! use smartcore::metrics::distance::minkowski::Minkowski;
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//!
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//! let x = vec![1., 1.];
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//! let y = vec![2., 2.];
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//!
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//! let l1: f64 = Minkowski::new(1).distance(&x, &y);
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//! let l2: f64 = Minkowski::new(2).distance(&x, &y);
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//!
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//! ```
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//! <script src="https://polyfill.io/v3/polyfill.min.js?features=es6"></script>
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//! <script id="MathJax-script" async src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-mml-chtml.js"></script>
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#[cfg(feature = "serde")]
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use serde::{Deserialize, Serialize};
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use std::marker::PhantomData;
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use crate::linalg::basic::arrays::ArrayView1;
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use crate::numbers::basenum::Number;
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use super::Distance;
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/// Defines the Minkowski distance of order `p`
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#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
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#[derive(Debug, Clone)]
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pub struct Minkowski<T: Number> {
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/// order, integer
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pub p: u16,
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_t: PhantomData<T>,
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}
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impl<T: Number> Minkowski<T> {
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/// instatiate the initial structure
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pub fn new(p: u16) -> Minkowski<T> {
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Minkowski { p, _t: PhantomData }
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}
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}
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impl<T: Number, A: ArrayView1<T>> Distance<A> for Minkowski<T> {
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fn distance(&self, x: &A, y: &A) -> f64 {
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if x.shape() != y.shape() {
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panic!("Input vector sizes are different");
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}
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if self.p < 1 {
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panic!("p must be at least 1");
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}
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let p_t = self.p as f64;
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let dist: f64 = x
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.iterator(0)
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.zip(y.iterator(0))
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.map(|(&a, &b)| (a - b).to_f64().unwrap().abs().powf(p_t))
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.sum();
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dist.powf(1f64 / p_t)
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[cfg_attr(
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all(target_arch = "wasm32", not(target_os = "wasi")),
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wasm_bindgen_test::wasm_bindgen_test
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)]
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#[test]
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fn minkowski_distance() {
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let a = vec![1., 2., 3.];
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let b = vec![4., 5., 6.];
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let l1: f64 = Minkowski::new(1).distance(&a, &b);
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let l2: f64 = Minkowski::new(2).distance(&a, &b);
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let l3: f64 = Minkowski::new(3).distance(&a, &b);
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assert!((l1 - 9.0).abs() < 1e-8);
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assert!((l2 - 5.19615242).abs() < 1e-8);
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assert!((l3 - 4.32674871).abs() < 1e-8);
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}
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#[test]
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#[should_panic(expected = "p must be at least 1")]
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fn minkowski_distance_negative_p() {
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let a = vec![1., 2., 3.];
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let b = vec![4., 5., 6.];
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let _: f64 = Minkowski::new(0).distance(&a, &b);
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}
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}
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