Hmm, I think the pretty traditional R style does the job... a = list(1,2,3) a[-2]
So I really do not see a good reason for doing a[2] = NULL instead of a = a[-2] Jeffrey J. Hallman wrote: >>From your tone, I gather you don't much like this behavior, and I can see your > point, as it not very intuitive that setting a list element to NULL deletes > any existing element at that index. But is there a better way to delete an > element from a list? Maybe there should be. > > Jeff > > Prof Brian Ripley <[EMAIL PROTECTED]> writes: >>> 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? >> Yes, it was apparently intended: R has long done this. >> >> x <- list(a=c(1L,2L), b=matrix(runif(4),2,2), c=LETTERS[1:3]) >> x[2] <- list(NULL) >> >> is what I think you are intending. >> >> See e.g. the comment in subassign.c >> >> /* If "val" is NULL, this is an element deletion */ >> /* if there is a match to "nlist" otherwise "x" */ >> /* is unchanged. The attributes need adjustment. */ > -- Dr Oleg Sklyar * EBI-EMBL, Cambridge CB10 1SD, UK * +44-1223-494466 ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
