unique.data.table could support list column same as unique.data.frame

[jangorecki]

It could support below case the same way as data.frame do, or if not support in data.table pkg then maybe redirects to data.frame method to perform expected operation instead of error.

library(data.table)
d1 <- data.table(l = list(list(letters[1:2]),list(Sys.time()),list(1:10),list(letters[1:2])))
unique(d1)
#Error in forderv(x, by = query$by, sort = FALSE, retGrp = TRUE) : 
#  First column being ordered is type 'list', not yet supported
unique(as.data.frame(d1))
#                               l
#1                          a, b
#2                    1437072565
#3 1, 2, 3, 4, 5, 6, 7, 8, 9, 10

[arunsrinivasan]

This'll be automatically taken care of when data.table:::forderv() can handle list columns (for which there's an issue somewhere).