Re: [Rd] assigning NULLs to elements of a list
:) Well, yes, but what do you do with a named vector if you want to remove an element by name? It is not general: you cannot do that on vectors, matrices, arrays and all inherited objects anyway. Using a negative index is a standard and throughout practice of deleting elements in R. Surely one can have exceptions or extended behaviour for different classes, like list and data.frame here, but I cannot say it is really necessary to have it in order to produce a clean, easily readable and reliable code. Yes, I know now, this NULL assignment has existed there for long time and I am not about to propose its removal, but I really do not see a good reason for having it either. I would never use it in my code either. After all you do not assign NULLs to elements of a non-list vector or matrix or array. Best, Oleg Gabor Grothendieck wrote: But what about by name? a - list(a = 1, b = 2, c = 3) a$b - NULL On Feb 13, 2008 9:39 AM, Oleg Sklyar [EMAIL PROTECTED] wrote: Hmm, I think the pretty traditional R style does the job... a = list(1,2,3) a[-2] So I really do not see a good reason for doing a[2] = NULL instead of a = a[-2] Jeffrey J. Hallman wrote: From your tone, I gather you don't much like this behavior, and I can see your point, as it not very intuitive that setting a list element to NULL deletes any existing element at that index. But is there a better way to delete an element from a list? Maybe there should be. Jeff Prof Brian Ripley [EMAIL PROTECTED] writes: I have just came across an (unexpected to me) behaviour of lists when assigning NULLs to list elements. I understand that a NULL is a valid R object, thus assigning a NULL to a list element should yield exactly the same result as assigning any other object. So I was surprised when assigning a NULL in fact removed the element from the list. Is this an intended behaviour? If so, does anybody know where is it documented and what is a good way around? Yes, it was apparently intended: R has long done this. x - list(a=c(1L,2L), b=matrix(runif(4),2,2), c=LETTERS[1:3]) x[2] - list(NULL) is what I think you are intending. See e.g. the comment in subassign.c /* If val is NULL, this is an element deletion */ /* if there is a match to nlist otherwise x */ /* is unchanged. The attributes need adjustment. */ -- Dr Oleg Sklyar * EBI-EMBL, Cambridge CB10 1SD, UK * +44-1223-494466 __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel -- Dr Oleg Sklyar * EBI-EMBL, Cambridge CB10 1SD, UK * +44-1223-494466 __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
Re: [Rd] assigning NULLs to elements of a list
But what about by name? a - list(a = 1, b = 2, c = 3) a$b - NULL On Feb 13, 2008 9:39 AM, Oleg Sklyar [EMAIL PROTECTED] wrote: 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 __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
Re: [Rd] assigning NULLs to elements of a list
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 __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
Re: [Rd] assigning NULLs to elements of a list
On Tue, 12 Feb 2008, Oleg Sklyar wrote: 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? Yes. If so, does anybody know where is it documented and what is a good way around? One place is FAQ 7.1 -thomas Thomas Lumley Assoc. Professor, Biostatistics [EMAIL PROTECTED] University of Washington, Seattle __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
Re: [Rd] assigning NULLs to elements of a list
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. */ -- Jeff __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
Re: [Rd] assigning NULLs to elements of a list
Oleg Sklyar wrote: 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? This topic is discussed in the R FAQ, in section 7.1 How can I set components of a list to NULL? It also shows up in section 3.3.3, in the context of incompatibilities with S. - Steve __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
Re: [Rd] assigning NULLs to elements of a list
On Tue, 12 Feb 2008, Oleg Sklyar wrote: 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? 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. */ 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 -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UKFax: +44 1865 272595 __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
Re: [Rd] assigning NULLs to elements of a list
On Tue, Feb 12, 2008 at 11:06:59AM +, Oleg Sklyar wrote: 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 Hi Oleg, To do this I use x[2] - list(NULL) In particular I do this when constructing lists to act as the 'what' argument for scan(), where a NULL element means that the column should be skipped, whereas obviously a non-existent element won't serve that purpose. I would be interested to hear whether this is the 'proper' way to construct such lists. Dan 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 __ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
[Rd] assigning NULLs to elements of a list
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
