R:如何删除data.table中的列？

Question

关于R包data.table的问题:如何以高效内存的方式删除多个data.table列？

假设要删除的列名存储在vector deleteCol中.

In a data.frame, it is:
DF <- DF[deleteCol] <- list()

对于data.table,我试过:

DT[, deleteCol, with=FALSE] <- list()

但这给了 unused argument(s) (with = FALSE)

Answer 1

好的,这里有几个选择.最后一个看起来正是你想要的......

 x<-1:5
 y<-1:5
 z<-1:5
 xy<-data.table(x,y,z)
 NEWxy<-subset(xy, select = -c(x,y) ) #removes column x and y

和

id<-c("x","y")
newxy<-xy[, id, with=FALSE]
newxy #gives just x and y e.g.

   #  x y
#[1,] 1 1
#[2,] 2 2
#[3,] 3 3
#[4,] 4 4
#[5,] 5 5

最后你真正想要的是什么:

anotherxy<-xy[,id:=NULL,with=FALSE] # removes comuns x and y that are in id

#     z
#[1,] 1
#[2,] 2
#[3,] 3
#[4,] 4
#[5,] 5