Thanks, Iâm actually more comfortable with vector-ish syntax than sql-ish but this is a good thing to keep in mind⦠I wonder how it compares in performance versus âbyâ or âtapplyâ
From: Gabor Grothendieck [via R] [mailto:ml-node+1461531-1948782...@n4.nabble.com] Sent: Wednesday, February 03, 2010 1:19 PM To: Steve Jaffe Subject: Re: tapply for function taking of >1 argument? Also try this: > library(sqldf) > DF <- data.frame(data = 1:10, groups = rep(1:2, 5), weights = 1) > sqldf("select groups, sum(data * weights)/sum(weights) 'wtd mean' from DF > group by groups") groups wtd mean 1 1 5 2 2 6 On Tue, Feb 2, 2010 at 5:06 PM, sjaffe <[hidden email]<http://n4.nabble.com/user/SendEmail.jtp?type=node&node=1461531&i=0>> wrote: > > Thanks! :-) > > I suppose it's obvious, but one will generally have to use a (anonymous) > function to 'unpack' the data.frame into columns, unless the function > already knows how to do this. > > I mention this because when I tested the solution on my example I got an > unexpected result -- apparently weighted.mean will operate on a 2-column > dataframe but not in the way one would expect. > > data = 1:10 > weights = rep(1,10) > groups = rep(c(1,2),5) > by( data.frame(data,weights), groups, weighted.mean) > groups: 1 > [1] 15 > ------------------------------------------------------------ > groups: 2 > [1] 17.5 >> > > > But > > by( data.frame(data,weights), groups, function(d) { weighted.mean(d[,1], > d[,2]) } ) > > does the right thing > > groups: 1 > [1] 5 > ------------------------------------------------------------ > groups: 2 > [1] 6 >> > > > > Bert Gunter wrote: >> >> ?by >> > >> Bert Gunter >> Genentech Nonclinical Statistics >> > -- > View this message in context: > http://n4.nabble.com/tapply-for-function-taking-of-1-argument-tp1460392p1460489.html > Sent from the R help mailing list archive at Nabble.com. > > [[alternative HTML version deleted]] > > ______________________________________________ > [hidden > email]<http://n4.nabble.com/user/SendEmail.jtp?type=node&node=1461531&i=1> > 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. > ______________________________________________ [hidden email]<http://n4.nabble.com/user/SendEmail.jtp?type=node&node=1461531&i=2> 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. ________________________________ View message @ http://n4.nabble.com/tapply-for-function-taking-of-1-argument-tp1460392p1461531.html To unsubscribe from Re: tapply for function taking of >1 argument?, click here< (link removed) ==>. -- View this message in context: http://n4.nabble.com/tapply-for-function-taking-of-1-argument-tp1460392p1461541.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.
