crowd_model.py 文件源码

def expectation_z(mu, var, L, w = 3):
    """
    USE LAPLACE approx
    Evaluate the expectation of log[ S(u)^L (1-S(u))^(1-L) ]
    when u ~ Normal(mu, var)
    """
    if L == 1:
        f = lambda u: np.log(S(u))
        fpp = lambda x: -np.exp(x) / pow(1 + np.exp(x), 2)
        return f(mu) + 0.5* fpp(mu)*var
    else:
        f = lambda u: np.log(1 - S(u))
        fpp = lambda x: -np.exp(x) / pow(1 + np.exp(x), 2)
        return f(mu) + 0.5* fpp(mu)*var

    # need: E[u~N](f)
    return scipy.integrate.quad(f, mu - w*std, mu + w*std)[0]