On Sun, Sep 30, 2012 at 10:51 AM, Salma Wafi <salmawaf...@yahoo.com> wrote: > Dear All, > Thank you very much for your kind and response. > > Actually, S(t) = exp(b* F(t)) represent one of survival models, where F(t) is > known cumulative distribtion function. So, that is why I need to generate the > survival times T based on this model. Then for generating time I have to > invert S(t) as following, > > Since, S(t) has uniform distribution on (0,1) so we can write that > U= exp(b*F(t)), where U is uniform (0,1). Now to generat the time t, we do > log(U)= b* F(t) > (log(U))/ b = F(t) and then t = F((log(U))/b)^(-1). > > Now in case F(t) is cdf of Lognormal distribution or Weibull distribution > > My Question is how we can get the inverse of the cumulative distribution > F(t) in R?. Is there any package in R can help to invert some function > especially if this function is pdf or cdf?.
I repeat myself: if you have fit F() to a log-normal or Weibull distribution, just use qlnorm() or qweibull() included in base R. If you still need to fit those distributions, use MASS::fitdistr. Cheers, Michael > > Thanks in advance. > [[alternative HTML version deleted]] > > > ______________________________________________ > R-help@r-project.org mailing list > 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. > ______________________________________________ R-help@r-project.org mailing list 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.
