R: how to subset a data.frame in a list and return data.frame?

Question

When subsetting a data.frame inside of a list, I get vectors instead of a data.frames (see the example below). How to avoid this and get a data.frames?

l <         


        

Answer 1

You need the ,drop=FALSE argument

> res <- lapply(l, function(x) x[2:nrow(x),, drop=FALSE])
> sapply(res,class)
           A            B            C 
"data.frame" "data.frame" "data.frame" 
> res
$A
  a
2 2
3 3

$B
  b
2 5
3 6
4 5

$C
  c
2 4
3 5
4 6