[datatable-help] POSIXct as data.table key

[Ken Williams]

Hi,

I see at https://r-forge.r-project.org/tracker/index.php?func=detail&aid=1482&group_id=240&atid=978 that POSIXct values are supported as key.  But I'm unsure how to efficiently query them.  Here are my attempts:

> library(lubridate)
> n <- now()
> d <- data.table(t=n+days(1:10), val=runif(10), key='t')
> d[n+days(1)]
Error in `[.data.table`(d, n + days(1)) :
  i has not evaluated to logical, integer or double
> d[n+days(1),]
Error in `[.data.table`(d, n + days(1), ) :
  i has not evaluated to logical, integer or double
> d[list(n+days(1)),]
Error in `[.data.table`(d, list(n + days(1)), ) :
  typeof x.t (integer) != typeof i.V1 (double)


I can query using a boolean, but I assume this is skipping the index on 't'?

> d[t==n+days(1),]
                       t       val
[1,] 2012-09-22 21:06:52 0.2550606


Thanks.


--
Ken Williams, Senior Research Scientist
WindLogics
http://windlogics.com


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