Message-Id: <34C536DE.5E78@redwood.rt.cs.boeing.com> Date: Tue, 20 Jan 1998 15:44:30 -0800 From: Fritz Scholz <scholz@redwood.rt.cs.boeing.com> To: r-help@stat.math.ethz.ch Subject: R-beta: questions and comments Let me first tell you that you and your cohorts are doing a great service to the statistical community with R. I have been working with Rseptbeta under Win95 and I am very impressed with its capabilities. I thought I give you some feedback gained from my limited playing with R. Fritz Scholz fritz.scholz@boeing.com ============================================================= When loading the Survival package, which is not yet supposed to work, it seems that glm does not work either. Without Survival glm seems to work. I am not sure whether this gives a clue concerning the problems with Survival. One interesting application is to Weibull data which is only observed at single inspection points T_1, ..., T_n, not all the same and contained in insp.times. The only thing that is known about the actual lifetimes X_1, ..., X_n is whether X_i < T_i or not, giving me the 0,1 vector status. One can then get the mle's of the Weibull scale (alpha) and shape (beta) parameters by using dat <- data.frame(status=status,insp.times=insp.times) out <- glm(status ~ log(insp.times), family=binomial(link=cloglog),data=dat). Then alpha <- exp(-out$coef[1]/out$coef[2]) and beta <- out$coef[2] will do it. I don't know whether this example usage is known in this form? ============================================================= The fix function seems to work on an existing object although I did not see it documented. However, a few times after repeated use of fix I was unable to write to a file on trying to exit. The only way out was to stop R without the ability to save the workspace. Can't quite make this reproducible yet, but it has happened a few times. ============================================================= In glm the offset does not seem to work. When I generate data like n <- 100 beta <- 2 x <- 5*(0:n)/n y <- x+beta*x+rnorm(n) dat <- data.frame(y=y,x=x) out1_glm.fit(x,y,family=gaussian(),offset=x,intercept=FALSE) out2_glm(y~x-1,family=gaussian,offset=x,data=dat) out_c(out1$coef,out2$coef) then out contains two numbers differing by 1, indicating that glm.fit seems to work and glm does not honor the offset. I was trying to implement the Weibull estimation routines as described in Chapter 13 of Gen. Lin. Models 2nd ed by McCullagh and Nelder, and that's when I ran into trouble with offset. ============================================================= Data entry It seems that xx <- de() works, whereas xx <- data.entry() does not, gives me xx=NULL on exit. ============================================================= -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-help-request@stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._