Fit time series Q(t) to a logistic function.

Inputs (vectors of same size): t (time) & Q

Outputs: Qpre (logistic model fit to data) and three independent parameters: thalf, Qinf, and a, describing the logistic

Q(t) = Qinf/(1 + exp(-a*(t-thalf)))

Qinf is value as t --> infinity

thalf is time of symmetric inflection point

a is time decay constant

Written by James Conder, Southern Illinois University, Oct. 2010