On 11/09/12 11:00, Matthew Dowle wrote:
Hi. I didn't know about base::comment. Should use unknownr::unk(),
shouldn't I!
Please raise a new feature request, or add it to this one :
#2197 "A simple labels attribute like in the Hmisc package for variable
descriptions"
https://r-forge.r-project.org/tracker/index.php?func=detail&aid=2197&group_id=240&atid=978
Do we want labels, or comments, or both? Griffith Rees (cc'd)?
I think we want column attributes. As in: all of them. The comment is
just one attribute. R uses attributes for all sorts of sneaky things so
I think it is a bad idea if we lose some of them some of the time.
Since comment<- will copy the whole table,
Even for column comments? I am not quite sure how that works.
we'd need setcomment() [or
setlabel(), or both] to avoid that copy; adding to the set* family.
A set attributes that allows setting column attributes may suffice.
PS: is stopifnot(identical(DT1[DT1]$A, DT1[DT1]$A.1)) a buglet?
Seems ok :
Sorry, my bad (because str(DT1[DT1]) lists them as having different
storage classes).
Allan
DT1 <- data.table(id = seq.int(1, 10), A = LETTERS[1:10], key = "id")
stopifnot(identical(DT1[DT1]$A, DT1[DT1]$A.1))
comment(DT1$A) <- "A"
stopifnot(identical(DT1[DT1]$A, DT1[DT1]$A.1))
Error: identical(DT1[DT1]$A, DT1[DT1]$A.1) is not TRUE
str(DT1[DT1]$A)
chr [1:10] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J"
str(DT1[DT1]$A.1)
atomic [1:10] A B C D ...
- attr(*, "comment")= chr "A"
On 11/09/12 09:47, I wrote:
I like comments, but [.data.table drops them, e.g.
More specifically, it drops them for the 'outer' data.table but not the
inner (!?) when doing the join:
DT1 <- data.table(id = seq.int(1, 10), A = LETTERS[1:10], key = "id")
comment(DT1$A) <- "A"
DT2 <- data.table(id = seq.int(2, 10, 2), b = letters[1:5], key = "id")
comment(DT2$b) <- "b"
str(DT1[DT2]) # No comment on A
str(DT2[DT1]) # No comment on b
Allan
PS: is stopifnot(identical(DT1[DT1]$A, DT1[DT1]$A.1)) a buglet?
DT1 <- data.table(A = 1:10)
comment(DT1$A) <- "Documenting A column"
DT2 <- DT1[A %% 2]
stopifnot(identical(comment(DT1$A), comment(DT2$A)))
Is there any way of preserving the comments? (My normal use case is
DT1 <- DT1[...] so copying from one to the other is a little ...
tedious?)
Allan
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