在 data.table 上使用 tail

Question

I'd like to use tail on a data.table like I do on a data frame. Is that possible? If not what's more efficient way to get the tail of a data table?

mainDF= data.frame(name= c("a","b","c","d"))
tail(mainDF,1)["name"]
dt<-as.data.table(mainDF)
setkey(dt, name )
tail(dt,1)["name"]

output

> mainDF= data.frame(name= c("a","b","c","d"))
> tail(mainDF,1)["name"]
  name
4    d
> dt<-as.data.table(mainDF)
> setkey(dt, name )
> tail(dt,1)["name"]
   name
1:   NA

Answer 1

在当前版本的data.table ，您可以非常接近：

tail(dt, 1L)[ , "name"]