[R] sample variogram construction

[matt.kowgier@utoronto.ca]

Hi

Im attempting to build a sample variogram for 300 obersvations
of longitudinal data. So what I need to do is compute the half 
squared differences  between pairs of residuals (for instance
if a subject has 4 obersvations, this is 4 choose 2 paird differences)
for each subject.
Also, then I need the corresponding time differences within each
individual. So the end result will be a 300 by 2 matrix with
columns corresponding to paired difference residuals within subject
and time differences within subject.
Basically im having trouble coding this kind of matrix in R,
if anyone can help me out or give me some tips id appreciate it.

Thanks.
Stuck in the for loop
student