The new function DT() used for chaining/piping drops data.frame rownames names

[Kamgang-B]

I noticed that the new function DT() drops row names when applied to data.frame.

df = mtcars[1:5, 1:2]
df
		   mpg cyl
Mazda RX4         21.0   6
Mazda RX4 Wag     21.0   6
Datsun 710        22.8   4
Hornet 4 Drive    21.4   6
Hornet Sportabout 18.7   8

df |> 
  DT(1:4, .SD)
  
   mpg cyl
1 21.0   6
2 21.0   6
3 22.8   4
4 21.4   6

[ecoRoland2]

I assume that's intended. data.table doesn't support row names (for good reasons).

[Kamgang-B]

Maybe I was not clear enough, Note that the input here is not a data.table but a data.frame (as apposed to data.table which is its extension). DT() works with data.frame's too (not only data.tables).

I personally think that the row names should be kept too since the input and output in this case support row names, and in my example it has row names.

The reasons you refer to are likely those specific to data.table.

[Kamgang-B]

Because DT() supports build-in data.frame (as opposed to data.table), I think it should also handle it appropriately.