[datatable-help] #4990 regarding

[Ricardo Saporta]

I think we should have a warning  iff  it is not a "clean" recycle  (ie,
the set gets cut off)

In other words

  if (length(longer) %% length(shorter) != 0)
     warning()



Ricardo Saporta
Graduate Student, Data Analytics
Rutgers University, New Jersey
e: saporta at rutgers.edu



On Mon, Oct 21, 2013 at 2:18 PM, Arunkumar Srinivasan <aragorn168b at gmail.com
> wrote:

>  Hi all,
>
> Here's the link to #4990: https://r-forge.r-**
> project.org/tracker/index.php?**func=detail&aid=4990&group_id=**
> 240&atid=975<https://r-forge.r-project.org/tracker/index.php?func=detail&aid=4990&group_id=240&atid=975>
>
> I'm not sure there should be any warning here. A warning message is
> created in `:=` if the RHS that's assigned is "bigger" in length than the
> LHS.
>
> For ex:
>
> dt <- data.table(a=rep(1:2, c(5,2)))
> dt[, b := c(1,2,3), by=a]
>
> # creates warning that RHS is of length 3 and LHS is of length 2 for a ==2.
> Warning message:
> In `[.data.table`(dt, , `:=`(b, c(1, 2, 3)), by = a) :
>   RHS 1 is length 3 (greater than the size (2) of group 2). The last 1
> element(s) will be discarded.
>
> Other than that, there need not be any warning because it's being
> recycled. For example,
>
> x <- 1:5
> x[c(TRUE, FALSE)]
> # [1] 1 3 5.
>
> Here, the number of elements of x are odd, but the recycling produces no
> warning. It may not exactly be the same issue, but to give an idea of
> silent recycling.
>
> What do you guys think?
>
> Arun
>
>
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