Returns likelihood of the measurement z given the Gaussian
    posterior (x, P) using measurement function H and measurement
    covariance error R

def likelihood(z, x, P, H, R):
    """
    Returns likelihood of the measurement z given the Gaussian
    posterior (x, P) using measurement function H and measurement
    covariance error R
    """
    return np.exp(log_likelihood(z, x, P, H, R))