I’m going to attempt to explain this without making any mistakes, but I’m betting this will attract a clarification or two in the comments.
A data frame is a list. When you subset a data frame using the name of a column and [
, what you’re getting is a sublist (or a sub data frame). If you want the actual atomic column, you could use [[
, or somewhat confusingly (to me) you could do aframe[,2]
which returns a vector, not a sublist.
So try running this sequence and maybe things will be clearer:
avector <- as.vector(aframe['a2'])
class(avector)
avector <- aframe[['a2']]
class(avector)
avector <- aframe[,2]
class(avector)