Function linear_discriminant_decode 

pub fn linear_discriminant_decode(
    train_data: &[f64],
    n_samples: usize,
    n_features: usize,
    labels: &[i64],
    test_point: &[f64],
) -> i64

Fisher linear discriminant decoder (Fisher 1936). train_data: (n_samples × n_features, row-major flat). labels: (n_samples,). test_point: (n_features,). Returns predicted class label.