Function observability_matrix 

pub fn observability_matrix(
    a: &[f64],
    c: &[f64],
    n: usize,
    p: usize,
) -> Vec<f64>

Compute the observability matrix [C; CA; CA^2; …].

a is n-by-n, c is p-by-n (flat row-major). Returns (n*p)-by-n.