I can get the interactions between factors like this:
> idx=c(1,3,6,9)
> jdx=idx
> levels(interaction(idx,jdx,lex.order=TRUE))
[1] "1.1" "1.3" "1.6" "1.9" "3.1" "3.3" "3.6" "3.9" "6.1" "6.3" "6.6"
"6.9"
[13] "9.1" "9.3" "9.6" "9.9"
This list contains all possible interactions. Whereas I need only the
combinations, e.g 4 over 2 = 6 total being
"1.3 " "1.6" "1.9" "3.6" "3.9" "6.9"
I have been unable to find how to get the combinations. Of course with
some string manipulations this can be done for this toy example. There
should be something in R to make this easy?
Thanks in advance
Alex van der Spek
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