Function random_hpd 

pub fn random_hpd<A, S>(n: usize) -> ArrayBase<S, Dim<[usize; 2]>>
where
    A: Scalar,
    S: DataOwned<Elem = A> + DataMut,

Random Hermite Positive-definite matrix

• Eigenvalue of matrix must be larger than 1 (thus non-singular)
• This function uses rand::thread_rng. See random_hpd_using for using another RNG.