java 逆逻辑函数/逆 Sigmoid 函数
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Inverse Logistic Function / Reverse Sigmoid Function
提问by schanq
I am currently coding up a fuzzy logic library in java. I have found the equations for all the standard functions - Grade, inverseGrade, Triangle, Trapezoid, Gaussian. However, I can't find the inverse of the sigmoid/ logistic function.
我目前正在用 java 编写一个模糊逻辑库。我找到了所有标准函数的方程 - Grade、inverseGrade、Triangle、Trapezoid、Gaussian。但是，我找不到 sigmoid/logistic 函数的逆函数。
The way I have written the logistic function is java is :
我编写逻辑函数的方式是 java 是：
//f(x) = 1/(1+e(-x))
public double logistic(double x){
return (1/(1+(Math.exp(-x)));
}
But I can't work out or find the inverse anywhere. My algebraic/calculus abilities are fairly limited, hence why I haven't been able to work out the inverse of the function.
但我无法在任何地方解决或找到逆。我的代数/微积分能力相当有限，因此我无法计算出函数的倒数。
Any hints or pointers would be a big help.
任何提示或指示都会有很大帮助。
Thanks
谢谢
回答by tom10
If
如果
y = 1/(1+exp(-x))
then
然后
x = ln(y/(1-y))
