survival_plot.py 文件源码

def fit(k):
    loss = 0.0
    for total_n, deltas in all_deltas:
        total_k = total_n
        P = 1.0
        for t in sorted(deltas.keys()):
            delta_k, delta_n = deltas[t]
            pred = total_n * math.exp(-k * t / YEAR)
            loss += (total_n * P - pred)**2
            P *= 1 + delta_k / total_n
            total_k += delta_k
            total_n += delta_n
    print(k, loss)
    return loss