A logistic function or logistic curve is a common S-shaped curve with the equation where For values of x {\displaystyle x} in the domain of real numbers from − ∞ {\displaystyle -\infty } to + ∞ {\displaystyle +\infty }, the S-curve shown on the right is obtained, with the graph of f {\displaystyle f} approaching L {\displaystyle L} as x {\displaystyle x} approaches + ∞ {\displaystyle +\infty } and approaching zero as x {\displaystyle x} approaches − ∞ {\displaystyle -\infty }. Wikipedia