[R-Forge #5296] Class lost when selecting columns

[arunsrinivasan]

Submitted by: Daniel Krizian; Assigned to: Arun ; R-Forge link

When selecting columns via j argument in [.data.table, the custom class is lost.

DT <- data.table(a=1:2,b=3:4)
setattr(DT, "class", c("newclass", class(DT)))

class(DT) # [1] "newclass"   "data.table" "data.frame"
class(DT[, list(a)]) # [1] "data.table" "data.frame"  ##### "newclass" lost

This might be related to #5293