> Calum wrote: > >> All of that is very nice so far. The I followed bits and pieces of >> other peoples posts in the past to plot on a weibull regression... >> >> > my_curve.Plac <- survreg( Surv(Survival, Censored==0)~ >> TreatmentGroup, subset=TreatmentGroup=="Placebo", data=TestData, >> dist='weibull')
Peter wrote: > I'd take a hard look at the pweibull(...) bit. Is "scale" really what > you want it to be? If coef(my_curve.Pred) is not a scalar, then it gets > recycled, which could easily cause oscillations. Aha - found it. Its from my attempt to subgroup the data before I discovered subset... I now have a curve instead of an oscillation. Now possibly that curve is wrong... will need to do more reading! For reference the line above should read: > my_curve.Plac <- survreg( Surv(Survival, Censored==0)~ 1, subset=TreatmentGroup=="Placebo", data=TestData, dist='weibull') >> Also is it possible to get an R-squared type value for the fit of this >> curve from someplace? >> >> Finally (three questions in one!) the first two censored data points >> (1 in each group) are actually lost to follow-ups. Should they be >> marked differently from censored? >> > Customarily they are not. (I'm sure it is possible to speculate at > length about it, though.) > Going off topic a bit - but did you mean customarily they are not censored or customarily they are not handled differently from censored! > Nothing spectacularly incompetent this far... (I'm not happy with R^2 > measures outside of linear models, or even within linear models, but > several well-reputed people do find them useful, so who am I to bicker?) I'm not competent to argue. But are you suggesting there is a better way to assess fit of the line to the data? Thats what I want - Not being a statistician I'm not fussed how its done. But If I'm going to extrapolate a line I'd like to know its a reasonable fit first (is that purely by eye?) There is a p value reported by survreg but no idea how to interpret it ;-) ______________________________________________ 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.
