Using “dat” from either of the answers above, try crossprod
and table
:
V <- crossprod(table(dat[1:2]))
diag(V) <- 0
V
# Items
# Items A B C D E F
# A 0 1 1 1 1 0
# B 1 0 3 1 1 1
# C 1 3 0 1 0 1
# D 1 1 1 0 1 1
# E 1 1 0 1 0 0
# F 0 1 1 1 0 0