David and Josh, Thanks very much for your help, it is much appreciated.
Peter On 12 Jan 2011, at 14:28, David Winsemius wrote: 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 > > ______________________________________________ > [email protected] mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. David Winsemius, MD West Hartford, CT ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
