1use rug::{
 2    Float,
 3    float::Round,
 4    ops::{AddAssignRound, DivAssignRound, SubAssignRound},
 5};
 6
 7use crate::layouts::{DataRef, VecZnx, ZnxInfos};
 8
 9impl<D: DataRef> VecZnx<D> {
10    pub fn std(&self, basek: usize, col: usize) -> f64 {
11        let prec: u32 = (self.size() * basek) as u32;
12        let mut data: Vec<Float> = (0..self.n()).map(|_| Float::with_val(prec, 0)).collect();
13        self.decode_vec_float(basek, col, &mut data);
14        // std = sqrt(sum((xi - avg)^2) / n)
15        let mut avg: Float = Float::with_val(prec, 0);
16        data.iter().for_each(|x| {
17            avg.add_assign_round(x, Round::Nearest);
18        });
19        avg.div_assign_round(Float::with_val(prec, data.len()), Round::Nearest);
20        data.iter_mut().for_each(|x| {
21            x.sub_assign_round(&avg, Round::Nearest);
22        });
23        let mut std: Float = Float::with_val(prec, 0);
24        data.iter().for_each(|x| std += x * x);
25        std.div_assign_round(Float::with_val(prec, data.len()), Round::Nearest);
26        std = std.sqrt();
27        std.to_f64()
28    }
29}