Hi Kynn: this oddity is discussed in Patrick Burn's document called "The R Inferno". I don't recall the fix so I'm not sure if below is the same as what his book says to do but it seems to do what you want. x <- list() x[[1]] <- 2 x length(x) print(str(x)) x[2] <- list(NULL) x length(x) print(str(x)) Still, I would look at that document rather than just using the above because I'm not an expeRt so there might be a better way ? Also, if you cant find Pat's website, let me know and I'll find it. I'm pretty sure that, if you google "Patrick Burns", his site should be up at the top and then his R-Inferno is easy to find from there. It's quite a useful document so I highly recommend it.
On May 22, 2009, Kynn Jones <kyn...@gmail.com> wrote: I'm an experienced programmer, but learning R is making me lose the little hair I have left... > list(NULL) [[1]] NULL > length(list(NULL)) [1] 1 > x <- list() > x[[1]] <- NULL > x list() > length(x) [1] 0 >From the above experiment, it is clear that, although one can create a one-element list consisting of a NULL element, one can't get the same result by assigning NULL to the first element of an empty list. And it gets worse: > x <- list(1, 2, 3) > length(x) [1] 3 > x[[2]] <- NULL > length(x) [1] 2 I just could NOT believe my eyes! Am I going crazy??? What I'm trying to do is so simple and straightforward: I want to be able to append NULL to a list, and, after the appending, have the last element of the list be NULL. Is that so unreasonable? How can it be done? TIA! Kynn [[alternative HTML version deleted]] ______________________________________________ [1]r-h...@r-project.org mailing list [2]https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide [3]http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. References 1. mailto:R-help@r-project.org 2. https://stat.ethz.ch/mailman/listinfo/r-help 3. http://www.R-project.org/posting-guide.html ______________________________________________ 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.