You can subset the `@data` slot which is a plain data frame, but its not always a good idea to access members of an object class via slots, in which case you can convert to a plain data frame with `as.data.frame`, which drops the geometry and gives back a plain data frame:

    bar_vector = as.data.frame(spfoo)[,"bar"]

One advantage of using `as.data.frame` instead of the slot is that this will also work if your spatial object is one of the new `sf` classes.