You can use the combn() function. I'll note that y is a vector, not a data frame.
combn(c(8,3,1,11,4,7), 2)
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11] [,12] [,13] [,14] [,15]
[1,] 8 8 8 8 8 3 3 3 3 1 1 1 11 11 4
[2,] 3 1 11 4 7 1 11 4 7 11 4 7 4 7 7