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.
