Hi you maybe could use paste
> f1<-sample(letters[1:3], 10, replace=T) > f2<-sample(letters[4:7], 10, replace=T) > f3<-sample(letters[9:11], 10, replace=T) > interaction(f1, f2, f3, drop=T) [1] c.e.j b.e.j a.e.j c.g.i a.f.j b.g.k a.e.i a.e.k a.d.j b.e.j Levels: a.e.i c.g.i a.d.j a.e.j b.e.j c.e.j a.f.j a.e.k b.g.k > paste(f1, f2, f3, sep=".") [1] "c.e.j" "b.e.j" "a.e.j" "c.g.i" "a.f.j" "b.g.k" "a.e.i" "a.e.k" "a.d.j" [10] "b.e.j" The difference is that interaction gives you directly factor, paste gives you character vector, but it may be convenient too for your purpose. Regards Petr > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-bounces@r- > project.org] On Behalf Of Arnaud Michel > Sent: Monday, July 22, 2013 10:57 AM > To: R help > Subject: [R] Calculate interaction for a big dataframe > > Hi > > To calculate the value of the interaction between factors of a > dataframe df, does exist any function which could replace the function > when the dataframe df has the numbers of rows of df is large (~55000) > and also the numbers of combinaison of the three factors is large. The > calcul abort. > The function to calculate the interaction is : > as.numeric(interaction(df [,c(1:3)],drop=TRUE)) > > To complete the question and to calculate interaction beetween 3 > factors f1, f2, f3, does it possible to calculate first f12 = > interaction > (f1,f2) and after calculate interaction (f12, f3). > It seems to me that yes. > > Thanks for your help > > > > > -- > Michel ARNAUD > Chargé de mission auprès du DRH > DGDRD-Drh - TA 174/04 > Av Agropolis 34398 Montpellier cedex 5 > tel : 04.67.61.75.38 > fax : 04.67.61.57.87 > port: 06.47.43.55.31 > > ______________________________________________ > 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. ______________________________________________ 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.
