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use serde::{Deserialize, Serialize};
use crate::linalg::BaseVector;
use crate::math::num::RealNumber;
#[derive(Serialize, Deserialize, Debug)]
pub struct R2 {}
impl R2 {
pub fn get_score<T: RealNumber, V: BaseVector<T>>(&self, y_true: &V, y_pred: &V) -> T {
if y_true.len() != y_pred.len() {
panic!(
"The vector sizes don't match: {} != {}",
y_true.len(),
y_pred.len()
);
}
let n = y_true.len();
let mut mean = T::zero();
for i in 0..n {
mean += y_true.get(i);
}
mean /= T::from_usize(n).unwrap();
let mut ss_tot = T::zero();
let mut ss_res = T::zero();
for i in 0..n {
let y_i = y_true.get(i);
let f_i = y_pred.get(i);
ss_tot += (y_i - mean).square();
ss_res += (y_i - f_i).square();
}
T::one() - (ss_res / ss_tot)
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn r2() {
let y_true: Vec<f64> = vec![3., -0.5, 2., 7.];
let y_pred: Vec<f64> = vec![2.5, 0.0, 2., 8.];
let score1: f64 = R2 {}.get_score(&y_true, &y_pred);
let score2: f64 = R2 {}.get_score(&y_true, &y_true);
assert!((score1 - 0.948608137).abs() < 1e-8);
assert!((score2 - 1.0).abs() < 1e-8);
}
}