[R] how to find unique pairs of variables?

[bby2103 at columbia.edu]

I have two variables, both numerical. I would like to find the unique  
values of the pairs, in other words, unique coordinates if I were to  
plot them.

I also need to know how many pairs there are, but I guess I can use  
length() if I can somehow isolate the unique pairs first?

Thanks a lot!

Bonnie Yuan