This constructs a list (vector) of random integers in R:
This makes a contingency table of the above data:
Since the corresponding R object (table) has non-trivial attributes, was used to make it possible to include those.
This constructs an R data frame out of the contingency table:
Here is the full internal form RLink uses to represent the above data frame:
As you can see, is now gone, since heads used in the RLink internal representation of R objects (RVector and RList) can accommodate attributes.
This creates a matrix:
Send it to R:
Assign another attribute to R's mat variable:
Get back a resulting R object:
Since now it has an attribute, was used to represent it. You can also display its attributes:
Note that the "dim" attribute is implicit in the matrix representation in the short form, so its presence does not require the use of . It is, however, explicitly present in the full form: