[datatable-help] data.table 1.8.2: Problem using by= and a key that doesn't match any rows in the table

[Matthew Dowle]

Yes this is a bug, already reported:  #2162 "Internal error with
simultanous join (with missing groups) and group by in 1.8.2"

https://r-forge.r-project.org/tracker/index.php?func=detail&aid=2162&group_id=240&atid=975

Will fix and add tests.  Thanks for reporting.  Have added link to your
example to the report.

Matthew

> I recently updated from data.table 1.7.1 to 1.8.2 and found that my old
> code using data.table
> no longer works.  I'm not sure if this is being caused by a bug in the new
> version of data.table
> or an intentional change to the way data.table works.
>
> In 1.7.1, I could do the following:
>> DT <- data.table(x=rep(c("a","b","c"),each=3), y=c(1,3,6), v=1:9)
>> setkey(DT, x)
>> DT[J(c("a", "b", "d")), sum(v), by=x]
>         x V1
> [1,]    a  6
> [2,]    b 15
> [3,] <NA> NA
>
>
> In 1.8.2, however, I get an error message:
>> DT <- data.table(x=rep(c("a","b","c"),each=3), y=c(1,3,6), v=1:9)
>> setkey(DT, x)
>> DT[J(c("a", "b", "d")), sum(v), by=x]
> Error in if (any(irows < 1L | irows > nrow(x))) stop("Internal error: some
> irows<1 or >nrow(x)") :
>   missing value where TRUE/FALSE needed
>
>
> Looking through the NEWS file I don't see any mention of this change (It's
> possible that I just missed it).
> If this an intentional change, I would ask that you consider reverting it.
>  It seems inconsistent that
> DT[J(c("a", "b", "d"))] adds a new row to the table, but DT[J(c("a", "b",
> "d")), sum(v), by=x]
> causes an error.
>
> Personally I think the following makes the most sense.  But just reverting
> back to what it did in 1.7.1
> seems better than having an error.
>> DT[J(c("a", "b", "d")), sum(v), by=x]
>      x V1
> [1,] a  6
> [2,] b 15
> [3,] d NA
>
>
> Thank you,
> Mike
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