[R] Sum Question

[Edgar Alminar]

Hello,
I have the following dataset (this is a piece of a much larger set):

     RID      SCRNO VISCODE RECNO CONTTIME
23    18 HBA0190012      bl     1        5
24    18 HBA0190012      bl     3        5
28    18 HBA0190012      bl     5        5
29    18 HBA0190012      bl     2        5
32    18 HBA0190012      bl     4        5
38    19 HBA0190013      bl     2       35
50    19 HBA0190013      bl     1        5
57    20 HBA0190014      bl     1       10
61    21 HBA0200015      bl     2       30
64    21 HBA0200015      bl     3       90
67    21 HBA0200015      bl     4       90
72    21 HBA0200015      bl     8        2
76    21 HBA0200015      bl     1       60
88    22 HBA0190016      bl     1       25
97    23 HBA0190017      bl     3       85
99    23 HBA0190017      bl     1        5
103   23 HBA0190017      bl     2        5
122   25 HBA0190019      bl     1       20
145   26 HBA0200020      bl     1       60
170   27 HBA0190021      bl     1        3
190   28 HBA0220022      bl     1       40
194   29 HBA0220023      bl     1       25
223   29 HBA0220023      bl     2       25

And I would like to output a list of the sums of CONTTIME for each SCRNO. What is the best way to do that? Any help would be greatly appreciated.

Thanks!
Edgar