I am using a logistic function to model observed response values (growth) as function of an input value:
$$\text{growth} = \displaystyle{\frac{A}{1+e^{\frac{k-\text{input}}{s}}}}$$
This functional form has lower asymptote of growth=$0$, but at input=$0$ it can assume a positive growth value.
I would like to use a similar sigmoid function with the constraint of growth=$0$ at input=$0$.
How can I modify the function?
I found this but it did not solve the problem: Logistic function passing through two points AND the origin?