My editorial opinion only: It will of necessity be slower (because there's more machinery underlying the sqldf package); but I doubt whether it would be noticeably slower than the native R solution in most practical situations. The same would be true for plyR's implementation (it relies on the proto package, which slows things down a bit).
The point is that the most important issue in almost all cases is the programmer's time to create and debug correct code, especially as the native machine speeds continue to increase. R gives you the option to choose whatever idiom you prefer to minimize this. The software implementation differences thereafter will rarely be important. In other words, pick your poison. Cheers, Bert Bert Gunter Genentech Nonclinical Biostatistics -----Original Message----- From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On Behalf Of sjaffe Sent: Wednesday, February 03, 2010 10:25 AM To: r-help@r-project.org Subject: Re: [R] tapply for function taking of >1 argument? Thanks, Ibm actually more comfortable with vector-ish syntax than sql-ish but this is a good thing to keep in mindb& I wonder how it compares in performance versus bbyb or btapplyb 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-tp1460392p1460 489.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-tp1460392p1461 531.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-tp1460392p1461 541.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.
