Hello,

Maybe there are simpler ways of doing it, but try the following.

sp <- lapply(split(dat, dat$id), function(.s){
     i <- min(which(.s$stat == 0), which(.s$g == 1))
     .s$d <- .s$stop[i]
     .s[-1][row(.s[-1]) >= i] <- NA
     .s
})

dat3 <- do.call(rbind, sp)
rownames(dat3) <- seq_len(nrow(dat3))
all.equal(dat2, dat3)  # only names are different


Hope this helps,

Rui Barradas

Em 17-09-2012 19:32, john james escreveu:
> Dear R users,
>   
> I have the following problems. My dataset (dat) is as follows:
>
> a <- c(1,2,3)
> id <- rep(a, c(3,2,3))
> stat <- c(1,1,0,1,0,1,1,1)
> g <- c(0,0,0,0,0,0,1,0)
> stop <- c(1,2,4,2,4,1,1.5,3)
> dat <- data.frame(id,stat,g,stop)
>   
> I want to creat a new dataset (dat2) with missing values
> such that when either g = =1 or stat = =0, the remaining rows for an
> individual subject is set to NA by using a new variable d (that states
> the exact time this
> happened from the stop variable). By this I mean dat2 that looks like,
>   
> id <- rep(a, c(3,2,3))
> sta2<- c(1,1,NA,1,NA,1,NA,NA)
> g2<- c(0,0,NA,0,NA,0,NA,NA)
> stop2 <- c(1,2,NA,2,NA,1,NA,NA)
> d <- c(4,4,NA,4,NA,1.5,NA,NA)
>   
> dat2 <- data.frame(id=id, stat2=sta2, g2=g2,stop2=stop2,d=d).
>   
> Thank you very much!
>   
> John
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>
>
>
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