A data frame with 100 observations, 5 variables,
and a special "cells"
attribute:
- A
Factor with levels 1, 2, and 3
- B
Factor with levels 1, 2, and 3
- C
Factor with levels 1, 2, and 3
- x
A numeric variable
- y
A numeric variable
In addition, attr(ubds, "cells")
consists of a named list of length 27 with the row numbers for
each combination of A, B, C
. For example,
attr(ubds, "cells")[["213"]]
has the row numbers corresponding
to levels A == 2, B == 1, C == 3
. The entries are ordered by
length, so the first entry is the cell with the lowest frequency.