[R] tree class in R?

[DFARRAR]

I am trying to store a couple numbers for each partition, in a subset of the 
partitions 
of my data set.  Of course, one can accomplish this using a binary tree.  (The 
first split is on 
inclusion/exclusion of the first object, and so on.)  I can probably simulate 
a tree using 
vectors.  (One vector gives the index of left child node, another the index of 
the right child node.)
However, it seems like there must be a useful class associated with the 
clustering 
or recursive partitioning procedures, perhaps not out there for everyone to 
see.  I poked around
on the R page and didn't see anything that clearly met my needs very directly.
 I hope I would not 
have to learn recursive partitioning in R to find what I need.