Dear developers: I have just came across an (unexpected to me) behaviour of lists when assigning NULLs to list elements. I understand that a NULL is a valid R object, thus assigning a NULL to a list element should yield exactly the same result as assigning any other object. So I was surprised when assigning a NULL in fact removed the element from the list. Is this an intended behaviour? If so, does anybody know where is it documented and what is a good way around?
Thanks for help, Oleg Sklyar Here goes an example, the inline C-code does exactly what I would prefer R were doing, but both R examples do remove the element 'b': x = list(a=c(1L,2L), b=matrix(runif(4),2,2), c=LETTERS[1:3]) library(inline) code=" SEXP res; PROTECT(res = Rf_duplicate(x)); SET_VECTOR_ELT(res,1,R_NilValue); UNPROTECT(1); return res; " setnull = cfunction(signature(x="list"),code) setnull(x) # $a # [1] 1 2 # $b # NULL # $c # [1] "A" "B" "C" y = x x[[2]] = NULL x # $a # [1] 1 2 # $c # [1] "A" "B" "C" x = y x$b = NULL x # $a # [1] 1 2 # $c # [1] "A" "B" "C" > sessionInfo() R version 2.6.1 (2007-11-26) i686-pc-linux-gnu locale: LC_CTYPE=en_GB.UTF-8;LC_NUMERIC=C;LC_TIME=en_GB.UTF-8;LC_COLLATE=en_GB.UTF-8;LC_MONETARY=en_GB.UTF-8;LC_MESSAGES=en_GB.UTF-8;LC_PAPER=en_GB.UTF-8;LC_NAME=C;LC_ADDRESS=C;LC_TELEPHONE=C;LC_MEASUREMENT=en_GB.UTF-8;LC_IDENTIFICATION=C attached base packages: [1] stats graphics grDevices utils datasets methods base other attached packages: [1] inline_0.3.3 loaded via a namespace (and not attached): [1] rcompgen_0.1-17 -- Dr Oleg Sklyar * EBI-EMBL, Cambridge CB10 1SD, UK * +44-1223-494466 ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
