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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