Solved – What are the differences between Logistic Function and Sigmoid Function

Question

Fig 1. Logistic Function

Fig 2. Sigmoid Function

is it more like generalized kind of sigmoid function where you could have a higher maximum value?

Answer 1

Yes, the sigmoid function is a special case of the Logistic function when $L=1$, $k=1$, $x_0 =0$.

If you play around with the parameters (Wolfram Alpha), you will see that

• $L$ is the maximum value the function can take. $e^{-k(x-x_0)}$ is always greater or equal than 0, so the maximum point is achieved when it it 0, and is at $L/1$.

• $x_0$ controls where on the $x$ axis the growth should the, because if you put $x_0$ in the function, $x_0 - x_0$ cancel out and $e^0 = 1$, so you end up with $f(x_0) = L/2$, the midpoint of the growth.

• the parameter $k$ controls how steep the change from the minimum to the maximum value is.