r - Unique combinations of two vectors without pair repetition -

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• select equivalent rows [a-b & b-a] 1 answer

i have problem need keep unique rows not have repeated pair e.g. if have table x1=c(1,2,3) , x2=c(2,1,3) first , third row kept. row (2,1) thrown out because (1,2) exists. can help?

thanks!

we can sort row using apply , logical index using duplicated remove duplicate rows.

 df1[!duplicated(t(apply(df1, 1, sort))),]  #   x1 x2  #1  1  2  #2  1  3  #3  1  1  #4  2  4  #6  2  2  #7  3  4  #8  3  2 

data

df1 <- structure(list(x1 = c(1l, 1l, 1l, 2l, 2l, 2l, 3l, 3l, 3l, 4l,  4l), x2 = c(2l, 3l, 1l, 4l, 1l, 2l, 4l, 2l, 1l, 2l, 2l)), .names = c("x1",  "x2"), class = "data.frame", row.names = c(na, -11l))