[R] how to sum multiple data entries for the same sampling event?

[karengrace84]

I'm having trouble with some catch per unit effort data (CPUE, fisheries
data). Some of the samples were "retained" and some "unretained," and they
are entered as 2 separate entries for the same sampling event (Date and
time). I want to calculate the total CPUE (so sum the "retained" and
"unretained" number for each sampling event) and am having troubld doing so.
Here's a sample of what my data.frame looks like now:

Date                               lmb.cpue              
Disposition.of.Catch
1999-07-10 12:10:00   0.66666667           Unretained
1999-07-10 12:10:00   0.16666667             Retained
1999-07-14 11:22:00   0.83333333           Unretained
1999-07-14 11:22:00   0.55555556             Retained
1999-07-14 11:48:00   0.16666667           Unretained
1999-07-14 11:48:00   0.58333333             Retained
1999-07-14 13:56:00   0.57142857             Retained
1999-07-15 10:23:00   0.11111111             Retained
1999-07-22 12:03:00   0.33333333             Retained
1999-07-25 11:26:00   0.40000000           Unretained
1999-07-25 11:26:00   1.00000000             Retained


And I would like to end up with:

Date                               lmb.cpue              
1999-07-10 12:10:00   0.83333333
1999-07-14 11:22:00   1.38888889
1999-07-14 11:48:00   0.75000000
1999-07-14 13:56:00   0.57142857
1999-07-15 10:23:00   0.11111111
1999-07-22 12:03:00   0.33333333
1999-07-25 11:26:00   1.40000000  

Thanks for any help you have to offer!        

--
View this message in context: http://r.789695.n4.nabble.com/how-to-sum-multiple-data-entries-for-the-same-sampling-event-tp4341670p4341670.html
Sent from the R help mailing list archive at Nabble.com.