Can some help me with a question on this bass model, please As I read some articles on this topic, I understand that 1. the bass formula is N(t) = pm + (q-p) N(t-1) - (q/m) (N(t-1))^2 2. which is a difference equation with the solution N(t) = m (1 − exp(−(p+q)t)) / (1 + (q/p)exp(−(p+q)t)) 3. So, using a linear regression would give us some some initial estimations for the parameters m, p, q 4. we then can put the initial estimations into a NLS to get the better estimations
Am I right? Now the question is, why is that I see people use cumulative data and try to fit it into a pdf as M * ( ((P+Q)^2 / P) * exp(-(P+Q) * T79) ) / (1+(Q/P)*exp(-(P+Q)*T79))^2, why not using the cumulative data and fit directly the N(t) [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.