Sometimes we take the hard road in data.table, to get to a better
place. Once bit64::integer64 is fully supported, it'll be much
easier. All the recent radix work for double applies almost
automatically to integer64 for example, but that radix work had to be
done first.
On 12/02/14 16:26, [email protected] wrote:
FYI (and this is a long outstanding argument) this is why I don't like
the bit64 package. These sorts of errors happen silently. I
understand that data.table can't use the other integer64 package, but
at least there it is obvious when things are being coerced.
In my situations, if I am grouping by a int64, it is usually either an
ID so I can just make it a character vector instead, or it is
something where I don't mind lost precision so I just make it numeric.
On Wed Feb 12 2014 at 11:22:40 AM, Matt Dowle <[email protected]
<mailto:[email protected]>> wrote:
Hi,
You're doing nothing wrong. Although you can load integer64 using
fread
and create them directly, data.table's grouping and keys don't
work on
them yet. Sorry, just not yet implemented. Because integer64 are
internally stored as type double (a good idea by package bit64),
data.table sees them internally as double and doesn't catch that the
type isn't supported yet (hence no error message such as you get for
type 'complex'). The particular integer64 numbers in this
example are
quite small so will use the lower bits. In double, those are the most
precise part of the significand, which would explain why only one
group
comes out here since data.table groups and joins floating point data
within tolerance.
Matt
On 06/02/14 23:38, Yike Lu wrote:
> After a long hiatus, I am back to using data.table. Unfortunately,
> I've encountered a problem. Am I doing something wrong here?
>
> require(data.table)
>
> dt = data.table(idx = 1:100 %% 3, 1:100)
> dt[, list(sum(V2)), by = idx]
> # normal
>
> require(bit64)
>
> dt2 = data.table(idx = integer64(100) + 1:100 %% 3, 1:100)
> dt2[, list(sum(V2)), by = idx]
> # only has one group:
> # idx V1
> #1: 1 5050
>
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