There are two functions you need to become familiar with:
?tapply
?ave
If you wanted these summed values to be placed in another column of
the same dataframe, you would use ave. If you wanted a new structure
(somewhat shorter) you would use tapply with sum as the function. E. g:
tapply(ecoregion$ED, ecoregion$ECOCODE, sum)
--
David.
On Jan 12, 2011, at 5:38 AM, Peter Francis wrote:
Dear List,
I have a question of convenience,
I am looking to sum the values of one column based on another column
- a example may help explain better!
ED ECOCODE
21.809467 AA0101
36.229566 PA1201
51.861284 PA1201
11.36232 PA1201
27.264634 PA1201
12.261986 PA1201
46.519313 PA1201
7.815376 PA1201
2.810428 PA1201
13.478372 PA1201
35.670182 PA1301
27.128715 AT0801
19.010294 AT1201
15.475368 AT1201
18.597983 AT0101
29.292615 AT0101
6.749846 AT0101
14.981488 AT0101
14.93511 AT0101
14.93511 AT0101
21.040785 AT0101
8.271615 AT0101
12.94232 AT0101
6.749846 AT0101
15.484412 AT0101
29.644494 AT0101
43.211212 AT0101
So for AA0101 it would be = 21.809467
AT1201 it would be = 19.010294+15.475368
etc
I would then like to be able to output a table with ECOCODE in one
column and the sum of ED in the other.
This is stored in a dataframe called ecoregion, i understand people
like having code to change but i have none as i am a relative
beginner! Sorry in advance!
Thanks
Peter
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
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David Winsemius, MD
West Hartford, CT
______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
