fn mean(&self) -> f64 {
        let mut xn = 0f64;
        let mut n = 0f64;

        for x in self.iter() {
            n += 1f64;
            xn += (x - xn) / n;
        }
        xn
    }
Mean

Uses welfords online algorithm for numerically stable computation.

# Examples
```
#[macro_use]
extern crate peroxide;
use peroxide::fuga::*;

fn main() {
let a = c!(1,2,3,4,5);
assert_eq!(a.mean(), 3.0);
}
```
src/statistics/stat.rs