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//! # Hamming Distance //! //! Hamming Distance measures the similarity between two integer-valued vectors of the same length. //! Given two vectors \\( x \in ℝ^n \\), \\( y \in ℝ^n \\) the hamming distance between \\( x \\) and \\( y \\), \\( d(x, y) \\), is the number of places where \\( x \\) and \\( y \\) differ. //! //! Example: //! //! ``` //! use smartcore::math::distance::Distance; //! use smartcore::math::distance::hamming::Hamming; //! //! let a = vec![1, 0, 0, 1, 0, 0, 1]; //! let b = vec![1, 1, 0, 0, 1, 0, 1]; //! //! let h: f64 = Hamming {}.distance(&a, &b); //! //! ``` //! //! <script src="https://polyfill.io/v3/polyfill.min.js?features=es6"></script> //! <script id="MathJax-script" async src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-mml-chtml.js"></script> use serde::{Deserialize, Serialize}; use crate::math::num::RealNumber; use super::Distance; /// While comparing two integer-valued vectors of equal length, Hamming distance is the number of bit positions in which the two bits are different #[derive(Serialize, Deserialize, Debug, Clone)] pub struct Hamming {} impl<T: PartialEq, F: RealNumber> Distance<Vec<T>, F> for Hamming { fn distance(&self, x: &Vec<T>, y: &Vec<T>) -> F { if x.len() != y.len() { panic!("Input vector sizes are different"); } let mut dist = 0; for i in 0..x.len() { if x[i] != y[i] { dist += 1; } } F::from_i64(dist).unwrap() / F::from_usize(x.len()).unwrap() } } #[cfg(test)] mod tests { use super::*; #[test] fn hamming_distance() { let a = vec![1, 0, 0, 1, 0, 0, 1]; let b = vec![1, 1, 0, 0, 1, 0, 1]; let h: f64 = Hamming {}.distance(&a, &b); assert!((h - 0.42857142).abs() < 1e-8); } }