fn col(&self, index: usize) -> Vec<C64> {
        assert!(index < self.col);
        let mut container: Vec<C64> = vec![Complex::zero(); self.row];
        for i in 0..self.row {
            container[i] = self[(i, index)];
        }
        container
    }
Extract Column

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

fn main() {
let a = cmatrix(vec![C64::new(1f64, 1f64),
C64::new(2f64, 2f64),
C64::new(3f64, 3f64),
C64::new(4f64, 4f64)],
2, 2, Row
);
assert_eq!(a.col(0), vec![C64::new(1f64, 1f64), C64::new(3f64, 3f64)]);
}
```
src/complex/matrix.rs