AFAICS this has essentially nothing to do with R. Please post elsewhere, e.g. on a statistics list like stats.stackexchange.com.
Cheers, Bert On Fri, May 29, 2015 at 6:44 AM, Abolfazl Saghafi < abolfazl.sagh...@gmail.com> wrote: > 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. [[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.
