[datatable-help] Can crash R with a data.table query

[mdowle at mdowle.plus.com]

I see that too now. It'll be inside dogroups.c. Harish - can you add as
bug please to tracker, good spot.  What should the result be though?  No
rows, for group "b", or NA?  The way the j is constructed it can't be 9.

Other ways to do that :

DT[A%in%c(25,85),sum(C),by=B]  # ok
     B  V1
[1,] a  67
[2,] b   9
[3,] c 905

DT[,.SD[A%in%c(85,25),sum(C)],by=B]  # ok
     B  V1
[1,] a  67
[2,] b   9
[3,] c 905

DT[,.SD[A==25,C]+.SD[A==85,C],by=B] # crash too

> setkey(DT,A)
> DT[J(c(25,85)),sum(C),by=B,mult="all"]  # ok, likely fastest
     B  V1
[1,] a  67
[2,] b   9
[3,] c 905



> That crashes R for me, too, somewhere in data.table.dll.
>
> - Tom
>
>
>
>
>> -----Original Message-----
>> From: datatable-help-bounces at lists.r-forge.r-project.org
>> [mailto:datatable-help-bounces at lists.r-forge.r-project.org]
>> On Behalf Of mdowle at mdowle.plus.com
>> Sent: Thursday, July 01, 2010 05:33
>> To: Harish
>> Cc: datatable-help at lists.r-forge.r-project.org
>> Subject: Re: [datatable-help] Can crash R with a data.table query
>>
>> What you mean by 'crash'? R simply stops or theres a message?
>> Try the clean install of latest 1.5, as per recent reply on
>> other thread, and can go from there...
>>
>> > Hi,
>> >
>> > I am crashing R with the following code (and it might have
>> something
>> > to do with data tables as well):
>> >
>> > =========
>> >
>> >
>> > DT <- structure(list(A = c(25L, 85L, 25L, 25L, 85L), B =
>> > structure(c(1L, 1L, 2L, 3L, 3L), .Label = c("a", "b", "c"),
>> class = "factor"),
>> >     C = c(2L, 65L, 9L, 82L, 823L)), .Names = c("A", "B",
>> "C"), class =
>> > c("data.table", "data.frame"), row.names = c(NA, -5L))
>> >
>> > DT[ , data.table( A, C )[ A==25, C ] + data.table( A, C )[
>> A==85, C ],
>> > by=B ]
>> >
>> > =========
>> >
>> > For every B, I am trying to sum the C's where A is 25 and 85.
>> >
>> > The crash has something to do with my row selection
>> criteria.  First,
>> > note that for B=="b", I don't have A==85.  It looks like a
>> numeric(0)
>> > is being returned in this case.
>> >
>> > In order to avoid the crash, I had to do something like:
>> >    if ( ! identical( DT[ blah ], numeric( 0 ) )
>> >
>> > It isn't just that R is unable to handle operations on numeric(0)
>> > because I don't get a crash when I just type in "numeric(0)
>> + 2".  So,
>> > my guess is that it has something to do with data.table as well.
>> >
>> >
>> > Harish
>> >
>> >
>> >
>> >
>> > _______________________________________________
>> > datatable-help mailing list
>> > datatable-help at lists.r-forge.r-project.org
>> >
>> https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable
>> > -help
>> >
>>
>>
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