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logistic 逻辑回归模型

1. sigmoid function (logistic function)

输出$f_{w,b}(x) = P(y=1|x;w,b)$：y 等于 1 的概率

[!NOTE]

如何理解？

​ When is $f_{w,b}(x) ≥ 0.5$

​ g(z) ≥ 0.5

​ z ≥ 0

​ w*x + b ≥ 0

决策边界: z = w*x+b = 0