Thanks everyone - this seems to be the most efficient answer, I'll do a bit of reading around too as suggested.
Thanks again, Ben Gillespie Research Postgraduate School of Geography University of Leeds Leeds LS2 9JT ________________________________________ From: D. Rizopoulos [d.rizopou...@erasmusmc.nl] Sent: 04 February 2013 09:35 To: Benjamin Gillespie Cc: r-help@r-project.org Subject: Re: [R] Script for conditional sums of vectors try this: a <- c(1,1,1,1,1,1,2,2,2,2,2,2) b <- c(1,1,1,2,3,4,1,1,2,2,3,4) c <- c(400,200,300,100,500,300,200,100,500,400,200,100) DF <- data.frame(a, b, c) with(DF, tapply(c, list(a, b), sum)) I hope it helps. Best, Dimitris On 2/4/2013 10:29 AM, Benjamin Gillespie wrote: > Hi guys, > > I hope you can help me with this (probably) simple query: > > I have a data frame: > > -------------------------- > > a=c(1,1,1,1,1,1,2,2,2,2,2,2) > b=c(1,1,1,2,3,4,1,1,2,2,3,4) > c=c(400,200,300,100,500,300,200,100,500,400,200,100) > > > data=data.frame(a=a,b=b,c=c) > > -------------------------- > > And I would like to get the following output: > > -------------------------- > > b > a 1 2 3 4 > 1 900 100 500 300 > 2 300 900 200 100 > > -------------------------- > > The values in the output represent the sum of values "c" in data frame > "data", for each "a" and "b" combination. > > For example, where "a" = 1 and "b" = 1, the output is 400+200+300 = 900. > > Please would anyone be able to provide a script to create my desired output? > > Many thanks in advance, > > Ben Gillespie > Research Postgraduate > > School of Geography > University of Leeds > Leeds > LS2 9JT > > > ______________________________________________ > 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. > -- Dimitris Rizopoulos Assistant Professor Department of Biostatistics Erasmus University Medical Center Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands Tel: +31/(0)10/7043478 Fax: +31/(0)10/7043014 Web: http://www.erasmusmc.nl/biostatistiek/ ______________________________________________ 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.
