[R] grouped colSums without for loops?

From: Hans Ekbrand <hans_at_sociologi.cjb.net>
Date: Tue, 18 Mar 2008 11:41:46 +0100


Consider the following data.frame, d.

d <- data.frame(c("a","b","c","d","b","a"), c(1,4,85,3,4,1), c(7,6,2,4,15,33)) names(d) <- c("foo", "bar", "baz")  

To get the colsum of d[[2]] for the rows that have d$foo == "a" I know I can use

colSums(subset(d, d[[1]] == "a", select = 2))

But what is needed to get a list of colSums for d[[2]] for each factor of d$foo ? Can it be done without a for loop?

-- 
Hans Ekbrand (http://sociologi.cjb.net) <hans@sociologi.cjb.net>
GPG Fingerprint: 1408 C8D5 1E7D 4C9C C27E 014F 7C2C 872A 7050 614E

______________________________________________ R-help_at_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.

Received on Tue 18 Mar 2008 - 10:45:16 GMT

Archive maintained by Robert King, hosted by the discipline of statistics at the University of Newcastle, Australia.
Archive generated by hypermail 2.2.0, at Tue 18 Mar 2008 - 11:30:22 GMT.

Mailing list information is available at https://stat.ethz.ch/mailman/listinfo/r-help. Please read the posting guide before posting to the list.

list of date sections of archive