136 lines
3.9 KiB
Rust
136 lines
3.9 KiB
Rust
//! # Precision score
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//!
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//! How many predicted items are relevant?
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//!
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//! \\[precision = \frac{tp}{tp + fp}\\]
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//!
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//! where tp (true positive) - correct result, fp (false positive) - unexpected result
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//!
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//! Example:
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//!
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//! ```
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//! use smartcore::metrics::precision::Precision;
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//! use smartcore::metrics::Metrics;
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//! let y_pred: Vec<f64> = vec![0., 1., 1., 0.];
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//! let y_true: Vec<f64> = vec![0., 0., 1., 1.];
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//!
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//! let score: f64 = Precision::new().get_score(&y_true, &y_pred);
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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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use std::collections::HashSet;
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use std::marker::PhantomData;
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#[cfg(feature = "serde")]
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use serde::{Deserialize, Serialize};
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use crate::linalg::basic::arrays::ArrayView1;
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use crate::numbers::realnum::RealNumber;
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use crate::metrics::Metrics;
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/// Precision metric.
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#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
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#[derive(Debug)]
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pub struct Precision<T> {
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_phantom: PhantomData<T>,
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}
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impl<T: RealNumber> Metrics<T> for Precision<T> {
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/// create a typed object to call Precision functions
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fn new() -> Self {
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Self {
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_phantom: PhantomData,
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}
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}
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fn new_with(_parameter: f64) -> Self {
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Self {
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_phantom: PhantomData,
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}
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}
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/// Calculated precision score
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/// * `y_true` - ground truth (correct) labels.
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/// * `y_pred` - predicted labels, as returned by a classifier.
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fn get_score(&self, y_true: &dyn ArrayView1<T>, y_pred: &dyn ArrayView1<T>) -> f64 {
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if y_true.shape() != y_pred.shape() {
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panic!(
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"The vector sizes don't match: {} != {}",
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y_true.shape(),
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y_pred.shape()
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);
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}
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let mut classes = HashSet::new();
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for i in 0..y_true.shape() {
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classes.insert(y_true.get(i).to_f64_bits());
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}
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let classes = classes.len();
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let mut tp = 0;
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let mut fp = 0;
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for i in 0..y_true.shape() {
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if y_pred.get(i) == y_true.get(i) {
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if classes == 2 {
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if *y_true.get(i) == T::one() {
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tp += 1;
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}
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} else {
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tp += 1;
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}
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} else if classes == 2 {
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if *y_true.get(i) == T::one() {
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fp += 1;
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}
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} else {
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fp += 1;
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}
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}
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tp as f64 / (tp as f64 + fp as f64)
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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 precision() {
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let y_true: Vec<f64> = vec![0., 1., 1., 0.];
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let y_pred: Vec<f64> = vec![0., 0., 1., 1.];
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let score1: f64 = Precision::new().get_score(&y_true, &y_pred);
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let score2: f64 = Precision::new().get_score(&y_pred, &y_pred);
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assert!((score1 - 0.5).abs() < 1e-8);
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assert!((score2 - 1.0).abs() < 1e-8);
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let y_true: Vec<f64> = vec![0., 1., 1., 0., 1., 0.];
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let y_pred: Vec<f64> = vec![0., 0., 1., 1., 1., 1.];
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let score3: f64 = Precision::new().get_score(&y_true, &y_pred);
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assert!((score3 - 0.6666666666).abs() < 1e-8);
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}
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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 precision_multiclass() {
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let y_true: Vec<f64> = vec![0., 0., 0., 1., 1., 1., 2., 2., 2.];
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let y_pred: Vec<f64> = vec![0., 1., 2., 0., 1., 2., 0., 1., 2.];
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let score1: f64 = Precision::new().get_score(&y_true, &y_pred);
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let score2: f64 = Precision::new().get_score(&y_pred, &y_pred);
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assert!((score1 - 0.333333333).abs() < 1e-8);
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assert!((score2 - 1.0).abs() < 1e-8);
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}
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}
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