Delete the dimensions of an rvar which are of size one. See base::drop()
Usage
# S4 method for rvar
drop(x)
Value
An rvar with the same length as x, but where any entry equal to 1
in dim(x) has been removed. The exception is if dim(x) == 1, in which
case dim(drop(x)) == 1 as well (this is because rvars, unlike numerics,
never have NULL dimensions).