Struct SequentialFeatureSelector 

pub struct SequentialFeatureSelector { /* private fields */ }

A greedy sequential feature selector.

Examples

use ferrolearn_preprocess::sequential_feature_selector::{
    SequentialFeatureSelector, Direction,
};
use ndarray::{array, Array1, Array2};

let sfs = SequentialFeatureSelector::new(1, Direction::Forward);
let x = array![[1.0, 10.0, 0.1],
                [2.0, 20.0, 0.2],
                [3.0, 30.0, 0.3]];
let y = array![1.0, 2.0, 3.0];

// Score function: sum of selected column means (higher is better)
let score_fn = |x_sub: &Array2<f64>, _y: &Array1<f64>| -> Result<f64, _> {
    let mean_sum: f64 = x_sub.columns().into_iter()
        .map(|c| c.sum() / c.len() as f64)
        .sum();
    Ok(mean_sum)
};

let fitted = sfs.fit(&x, &y, score_fn).unwrap();
assert_eq!(fitted.selected_indices().len(), 1);
// Feature 1 (column means 10,20,30 → mean 20) should be selected
assert_eq!(fitted.selected_indices(), &[1]);

Implementations

impl SequentialFeatureSelector

pub fn new(n_features_to_select: usize, direction: Direction) -> Self

Create a new SequentialFeatureSelector.

Parameters

• n_features_to_select — how many features to keep.
• direction — Direction::Forward or Direction::Backward.

pub fn n_features_to_select(&self) -> usize

Return the number of features to select.

pub fn direction(&self) -> Direction

Return the search direction.

pub fn fit<F: Float + Send + Sync + 'static>( &self, x: &Array2<F>, y: &Array1<F>, score_fn: impl Fn(&Array2<F>, &Array1<F>) -> Result<F, FerroError>, ) -> Result<FittedSequentialFeatureSelector<F>, FerroError>

Fit the selector by evaluating feature subsets with a scoring function.

Parameters

• x — the feature matrix (n_samples x n_features).
• y — the target vector (n_samples).
• score_fn — a callback (&Array2<F>, &Array1<F>) -> Result<F, FerroError> that evaluates the quality of a feature subset.

Errors

• FerroError::InvalidParameter if n_features_to_select is zero or exceeds the number of features.
• FerroError::ShapeMismatch if x and y have mismatched lengths.
• Propagates errors from score_fn.

Trait Implementations

impl Clone for SequentialFeatureSelector

fn clone(&self) -> SequentialFeatureSelector

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for SequentialFeatureSelector

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.