Or with ddply : library(plyr) dat <- structure(list(ED = c(21.809467, 36.229566, 51.861284, 11.36232, 27.264634, 12.261986, 46.519313, 7.815376, 2.810428, 13.478372, 35.670182, 27.128715, 19.010294, 15.475368, 18.597983, 29.292615, 6.749846, 14.981488, 14.93511, 14.93511, 21.040785, 8.271615, 12.94232, 6.749846, 15.484412, 29.644494, 43.211212), ECOCODE = structure(c(1L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 6L, 3L, 4L, 4L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L), .Label = c("AA0101", "AT0101", "AT0801", "AT1201", "PA1201", "PA1301"), class = "factor")), .Names = c("ED", "ECOCODE"), class = "data.frame", row.names = c(NA, -27L)) dat ddply(dat,"ECOCODE",summarise,EDsummed=sum(ED)) Felipe D. Carrillo Supervisory Fishery Biologist Department of the Interior US Fish & Wildlife Service California, USA http://www.fws.gov/redbluff/rbdd_jsmp.aspx
----- Original Message ---- > From: Peter Francis <peterfran...@me.com> > To: r-help@r-project.org > Sent: Wed, January 12, 2011 2:38:19 AM > Subject: [R] Sum by column > > 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 > > ______________________________________________ > R-help@r-project.org 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. > ______________________________________________ R-help@r-project.org 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.