Many thanks - this is very helpful indeed! Best wishes, Jeremy
On 15 Jun 2011, at 21:58, Daniel Malter [via R] wrote: x<-c(1,1,1,1,1,2,2,2,2,2) y<-rnorm(10) z<-y+rnorm(10) by(data.frame(y,z),factor(x),cor) hth, Daniel jfdawson wrote: I'm hoping there is a simple answer to this - it seems that there should be, but I can't figure it out. I have a matrix/data frame with three variables of interest - V1, V2, V3. One, V1, is a factor with x levels (x may be a large number); I want to calculate the correlation between the other two (i.e. cor(V2,V3)) for each level, and store it as a vector of length x. I should think this should be possible using a function like tapply, but I cannot work out what the syntax would be - everything I have tried produces either an error, or just repeats the correlations between V2 & V3 on the whole matrix. Could anyone suggest what I should be doing? Many thanks, Jeremy ________________________________ If you reply to this email, your message will be added to the discussion below: http://r.789695.n4.nabble.com/Correlations-by-subgroups-tp3599548p3600553.html To unsubscribe from Correlations by subgroups, click here<http://r.789695.n4.nabble.com/template/NamlServlet.jtp?macro=unsubscribe_by_code&node=3599548&code=ai5mLmRhd3NvbkBhc3Rvbi5hYy51a3wzNTk5NTQ4fC03NTUwNzA2NTM=>. -- View this message in context: http://r.789695.n4.nabble.com/Correlations-by-subgroups-tp3599548p3600692.html Sent from the R help mailing list archive at Nabble.com. [[alternative HTML version deleted]] ______________________________________________ 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.
