is_subset: Determine whether the first vector is a subset of the second vector
Description
Determine whether the first vector is a subset of the second vector
Usage
is_subset(x, y)
Value
TRUE if x is a subset of y, or FALSE otherwise. x is
considered a subset of y if all elements of x are also in y,
i.e., if setdiff(x, y) is a vector of length 0.