[R] Dataframe manipulation question

[Greg Blevins]

Hello,

I have a data frame that has three fields.

Resp#     ActCode     ProdUsed
100          3                  2
100          3                  2
100          4                  3
100          4                  3
101          3                  6
102          2                  1
102          3                  1
103          5                  1
103          5                  1
103          3                  2
103          3                  2
104          3                  1

What I seek to do.

If a row following a row is identical for the fields Resp3 and ActCode, I
then want to delete one of the two matching rows. Based on this logic, the
resulting df would look like that shown below.

Resp# ActCode    ProdUsed
100      3           2
100      4           3
101      3           6
102      2           1
102      3           1
103      5           1
103      3           2
104      3           1

I have tried match, tried to write something that if the current row minus
the previous row equal 0 for both Resp# and ActCode, then delete the row,
but to no avail.  Not knowing what to search on for this problem, I turn to
the R experts for help.

(Windows 2000, R 2.0, 384 meg memory)
Greg Blevins
The Market Solutions Group