cfbd45bfc0
* Improve features * Add wasm32-wasi as a target * Update .github/workflows/ci.yml Co-authored-by: morenol <22335041+morenol@users.noreply.github.com>
93 lines
2.3 KiB
Rust
93 lines
2.3 KiB
Rust
//! # Euclidian Metric Distance
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//!
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//! The Euclidean distance (L2) between two points \\( x \\) and \\( y \\) in n-space is defined as
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//!
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//! \\[ d(x, y) = \sqrt{\sum_{i=1}^n (x-y)^2} \\]
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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::euclidian::Euclidian;
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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 l2: f64 = Euclidian::new().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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/// Euclidean distance is a measure of the true straight line distance between two points in Euclidean n-space.
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#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
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#[derive(Debug, Clone)]
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pub struct Euclidian<T> {
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_t: PhantomData<T>,
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}
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impl<T: Number> Default for Euclidian<T> {
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fn default() -> Self {
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Self::new()
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}
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}
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impl<T: Number> Euclidian<T> {
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/// instatiate the initial structure
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pub fn new() -> Euclidian<T> {
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Euclidian { _t: PhantomData }
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}
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/// return sum of squared distances
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#[inline]
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pub(crate) fn squared_distance<A: ArrayView1<T>>(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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let sum: f64 = x
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.iterator(0)
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.zip(y.iterator(0))
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.map(|(&a, &b)| {
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let r = a - b;
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(r * r).to_f64().unwrap()
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})
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.sum();
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sum
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}
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}
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impl<T: Number, A: ArrayView1<T>> Distance<A> for Euclidian<T> {
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fn distance(&self, x: &A, y: &A) -> f64 {
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Euclidian::squared_distance(x, y).sqrt()
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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 squared_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 l2: f64 = Euclidian::new().distance(&a, &b);
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assert!((l2 - 5.19615242).abs() < 1e-8);
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}
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}
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