Logistic function

"The logistic equation (sometimes called the Verhulst model or logistic growth curve) is a model of population growth first published by Pierre Verhulst (1845, 1847). The model is continuous in time."

See


 * 1) Logistic Equation at Wolfram MathWorld
 * 2) Fitting a logistic curve to data with Matlab
 * 3) Fitting a logistic curve to data with Excel