That's odd. Please provide result of sessionInfo() and str(DT).
Matthew
On 09.04.2013 11:32, David Bellot wrote:
> Hi,
>
> I have
a data.table DT with one of the column named x and I other names, let's
say, a1, a2, ... aN. The key of this data.table is made of a1...aN.
>
>
Later on, I aggregate my DT with x like this:
> agg = DT[ ,
list(m=mean(y), c=length(y)), by = c("x") ]
>
> The problem is that "x"
has 331 unique values as found by length(unique(DT$x)) but my result
"agg" only has 119 rows. I tried by changing the key to "x" alone but
the problem persists. My DT table has a few millions rows by the way.
>
> I'm sure I'm missing something totally obvious :-( !!!!
>
> Any idea
?
> Best,
> David
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