Thank you for the input. The FAQ indicates:
How can I set components of a list to NULL? I wanted to detect if an element is NULL or missing. I have come up with a work-around that seems to work. Maybe others will have a better way: if(length(rlist) < index || is.null(rlist[[index]])) I knew that [[]] gave me the element at the specified index but I kept running into a error that the index was out of bounds. So, I put in the first test. So if I am testing for the 4th elemant and only element 3 has been set this will detext that the list is not that long and considers it a NULL element. Kevin ---- Wacek Kusnierczyk <[EMAIL PROTECTED]> wrote: > Erik Iverson wrote: > > FYI, this is FAQ 7.1 > > ... which says what you should and should not do, but without any a > justification for the design. coherently, x[i] = list(NULL) should do > the same as x[[i]] = NULL, if only for symmetry with x[i] = list(1) and > x[[1]] = 1, for example. > > vQ > > > > > Wacek Kusnierczyk wrote: > >> Barry Rowlingson wrote: > >>> 2008/11/3 <[EMAIL PROTECTED]>: > >>> > >>> > >>>> So how do I detect the NULL at r[1]? > >>>> > >>> How can you detect what is not there? > >>> > >>> Single square brackets on a list give you a list. Double square > >>> brackets give you the elements. > >>> > >>> is.null(r[[1]]) should be TRUE. > >>> > >> > >> interestingly: > >> > >> (l = list(1, NULL)) > >> [[1]] > >> [1] 1 > >> > >> [[2]] > >> NULL > >> > >> > >> l = list(1); l[[2]] = NULL; l > >> [[1]] > >> [1] 1 > >> > >> > >> l = as.list(1:3); l[[2]] = NULL; l > >> [[1]] > >> [1] 1 > >> > >> [[2]] > >> [1] 2 > >> > >> > >> you can have NULL as an element on a list, but assigning NULL to an > >> element of a list removes the element rather than makes it a NULL. > >> i find it more coherent if l[i] would remove the element (as it does) > >> while l[[i]] would assign NULL to it (as it doesn't), OR if list(1, > >> NULL) would return a list of 1 element. note, x = NULL *assigns* NULL > >> to x rather than removes x: > >> > >> x > >> Error: object "x" not found > >> > >> x = NULL; x > >> NULL > >> > >> vQ > >> > >> ______________________________________________ > >> 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. > > > -- > ------------------------------------------------------------------------------- > Wacek Kusnierczyk, MD PhD > > Email: [EMAIL PROTECTED] > Phone: +47 73591875, +47 72574609 > > Department of Computer and Information Science (IDI) > Faculty of Information Technology, Mathematics and Electrical Engineering > (IME) > Norwegian University of Science and Technology (NTNU) > Sem Saelands vei 7, 7491 Trondheim, Norway > Room itv303 > > Bioinformatics & Gene Regulation Group > Department of Cancer Research and Molecular Medicine (IKM) > Faculty of Medicine (DMF) > Norwegian University of Science and Technology (NTNU) > Laboratory Center, Erling Skjalgsons gt. 1, 7030 Trondheim, Norway > Room 231.05.060 > > ______________________________________________ > 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. ______________________________________________ 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.