On 11-Apr-2012 16:28:31 Christopher Kelvin wrote: > Hello, > can i implement this as 10% censored data where t gives me > failure and x censored. > Thank you > > p=2;b=120 > n=50 > > set.seed(132); > r<-sample(1:50,45) > t<-rweibull(r,shape=p,scale=b) > t > set.seed(123);_ > cens <- sample(1:50, 5)_ > x<-runif(cens,shape=p,scale=b)_ > x > > Chris Guure > Researcher, > Institute for Mathematical Research > UPM
This query is obscure! First, its approach does not seem to conform to the standard notion of "censored data". This refers to a situation where, for each item observed, either (a) it value falls within a certain range (which may itself depend on the item), in which case its value is recorded as a value in the data; or (b) its value falls outside that range, in which case that fact is recorded but the value is not recorded (thus being "censored"). Eaxmple: Patients who have been admitted to hospital for a particular disease are subsequently monitored for a period of time (days/months/years) which may vary from patient to patient. The reason for the time limitation may be that the design of the investigation set a limit, or may be haphazard as a result of the patient moving away and no longer being accessible. The value recorded (if available) is the time from admission to death. If not available, then all that can be recorded is that the event occurred later than the upper time limit for thaqt patient. As far as I can see, no element of your code above corresponds to this notion of "censored". Next, your "r<-sample(1:50,45)" selects 45 different values from (1:50), and then your "t<-rweibull(r,shape=p,scale=b)" generates 45 values sampled from the Weibull distribution, ** regardless of the 45 values from (1:50) in r ** -- See under '?rweibull' where it says: "n: number of observations. If 'length(n) > 1', the length is taken to be the number required." So it would seem that your "r<-sample(1:50,45)" is superfluous, and you could simply have written "t<-rweibull(45,shape=p,scale=b)". Similar comments apply to your cens <- sample(1:50, 5) x<-runif(cens,shape=p,scale=b) where you could have equivalently written "x<-runif(5,shape=p,scale=b)". Also, the parameters "shape" and "scale" would not be recognised by runif(), whose parameters are as in "runif(n, min=..., max=...)". Maybe you meant to write "x<-rweibull(cens,shape=p,scale=b)", but then you would simply be sampling a further 5 values from the same Weibull distribution, along with your original 45. So how does censoring come into this? If you would explain, in plain words, what you are seeking to do, it would help to remove this obscurity and confusion! Hoping this helps, Ted. ------------------------------------------------- E-Mail: (Ted Harding) <ted.hard...@wlandres.net> Date: 11-Apr-2012 Time: 23:23:36 This message was sent by XFMail ______________________________________________ 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.
