Hello,
Try the following.
(I've changed your function a bit. And named the data.frame 'dat', not
'data', which is an R function.)
myfun <- function (x) ifelse(sum(x) == 0, 0, x/sum(x))
aggregate(Count ~ Trip_id + Length + CommonName, data = dat, myfun)
The output shows that each and every group corresponds to a single row
of the original df. The 1's represent 100%, myfun _is_ dividing by
sum(Count) Trip_id/Length/CommonName group. If you want just
Trip_id/CommonName, use
aggregate(Count ~ Trip_id + CommonName, data = dat, myfun)
Or use your instruction without 'Length' in the by list:
b <- with(dat, aggregate(x=list(Percent=Count),
by=list(Trip_id=Trip_id, Species=CommonName),
FUN = myfun))
b
Trip_id Species Percent
1 230 Alewife 0.01408451
2 230 Herring,Blueback 0.11111111
3 230 Shad,American 0.09090909
4 231 Shad,American 0.14285714
As you can see, the results are the same, with different output colnames.
Hope this helps,
Rui Barradas
Em 25-10-2012 15:19, Sally_roman escreveu:
Hi -I am using R v 2.13.0. I am trying to use the aggregate function to
calculate the percent at length for each Trip_id and CommonName. Here is a
small subset of the data.
Trip_id Vessel CommonName Length Count
1 230 Sunlight Shad,American 19 1
2 230 Sunlight Shad,American 20 1
3 230 Sunlight Shad,American 21 1
4 230 Sunlight Shad,American 23 1
5 230 Sunlight Shad,American 26 1
6 230 Sunlight Shad,American 27 1
7 230 Sunlight Shad,American 30 2
8 230 Sunlight Shad,American 33 1
9 230 Sunlight Shad,American 34 1
10 230 Sunlight Shad,American 37 1
11 230 Sunlight Herring,Blueback 20 1
12 230 Sunlight Herring,Blueback 21 2
13 230 Sunlight Herring,Blueback 22 5
14 230 Sunlight Herring,Blueback 26 1
15 230 Sunlight Alewife 17 1
16 230 Sunlight Alewife 18 1
17 230 Sunlight Alewife 20 2
18 230 Sunlight Alewife 21 4
19 230 Sunlight Alewife 22 16
20 230 Sunlight Alewife 23 22
21 230 Sunlight Alewife 24 16
22 230 Sunlight Alewife 25 4
23 230 Sunlight Alewife 26 1
24 230 Sunlight Alewife 27 2
25 230 Sunlight Alewife 28 2
26 231 Western Venture Shad,American 23 1
27 231 Western Venture Shad,American 24 1
28 231 Western Venture Shad,American 25 1
29 231 Western Venture Shad,American 28 2
30 231 Western Venture Shad,American 29 2
My code is:
myfun<-function (x) x/sum(x)
b<-with(data,aggregate(x=list(Percent=Count),by=list(Trip_id=Trip_id,Length=Length,Species=CommonName),
FUN="myfun"))
My issue is that the percent is not be calculated by Trip_id and CommonName.
The result is that each row has a percent of 1 indicating that myfun is not
dividing by the sum of counts with a Trip_id/CommonName group. Any help
would be appreciated.
Thank you
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