Hi,
I have longitudinal school suspension data on students. I would like to
figure out how many students (id_r) have no suspensions (sus), i.e. have a
code of '0'. My data is in long format and the first 20 records look like
the following:

> suslm[1:20,c(1,7)]
   id_r sus
   11   0
   15  10
   16   0
   18   0
   19   0
   19   0
   20   0
   21   0
   21   0
   22   0
   24   0
   24   0
   25   3
   26   0
   26   0
   30   0
   30   0
   31   0
   32   0
   33   0

Each id_r is unique and I'd like to know the number of id_r that have a 0
for sus not the total number of 0. Does that make sense?
Thanks!
Chris

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