[R] Calculate interaction for a big dataframe

[PIKAL Petr]

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-bounces at r-project.org [mailto:r-help-bounces at 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
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