Function pack_stats

crates/openquant/src/feature_importance.rs:353–362

(feature_names: &[String], values: &[Vec<f64>])

}

fn pack_stats(feature_names: &[String], values: &[Vec<f64>]) -> BTreeMap<String, ImportanceStats> {
    let mut out = BTreeMap::new();
    for (j, name) in feature_names.iter().enumerate() {
        let (m, s) = mean_std(&values[j]);
        let mean = if m.is_finite() { m } else { 0.0 };
        let std = if s.is_finite() { s * (values[j].len() as f64).powf(-0.5) } else { 0.0 };
        out.insert(name.clone(), ImportanceStats { mean, std });
    }
    out
}

fn nan_mean_std(v: &[f64]) -> (f64, f64) {
    let vals: Vec<f64> = v.iter().copied().filter(|x| x.is_finite()).collect();