[datatable-help] zero length list component in j

[Gabor Grothendieck]

In the first case it replaced the zero length component with NA and in
the second case it did not.  Why the difference?

On Fri, May 17, 2013 at 4:33 PM, Eduard Antonyan
<eduard.antonyan at gmail.com> wrote:
> Maybe I'm missing smth, but what else did you expect? Looks like it did it's
> best to compensate for the user not supplying full data in the first
> example, and there really was nothing to do in the second one.
>
>
>
> On Fri, May 17, 2013 at 3:27 PM, Gabor Grothendieck
> <ggrothendieck at gmail.com> wrote:
>>
>> Is this intended?  If we use j = list(x = "X", y = numeric(0)) we get
>> a row but if we use just list(y = numeric(0)) then we do not get a
>> row.  In the first case it filled in the zero length component with NA
>> and in the second case it just omitted the row entirely:
>>
>> > dd <- data.table(a = 1:3)
>> > dd
>>    a
>> 1: 1
>> 2: 2
>> 3: 3
>> > dd[, list(x = "X", y = numeric(0)), by = a]
>>    a x  y
>> 1: 1 X NA
>> 2: 2 X NA
>> 3: 3 X NA
>> > dd[, list(y = numeric(0)), by = a]
>> Empty data.table (0 rows) of 2 cols: a,y
>>
>>
>> --
>> Statistics & Software Consulting
>> GKX Group, GKX Associates Inc.
>> tel: 1-877-GKX-GROUP
>> email: ggrothendieck at gmail.com
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>>
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>
>



--
Statistics & Software Consulting
GKX Group, GKX Associates Inc.
tel: 1-877-GKX-GROUP
email: ggrothendieck at gmail.com