[R] create a pairwise coocurrence matrix

Stefan Evert stefanML at collocations.de
Thu Nov 11 10:44:31 CET 2010

If I understood you correctly, you have this matrix of indicator variables for occurrences of terms in documents:

  A <- matrix(c(1,1,0,0,1,1,1,0,1,1,1,0,0,0,1), nrow=3, byrow=TRUE, dimnames=list(paste("doc",1:3), paste("term",1:5)))

and want to determine co-occurrence counts for pairs of terms, right? (The formatting of your matrices was messed up, and some of your co-occurrence counts don't make sense to me.)

The fastest and easiest solution is

  t(A) %*% A

Hope this helps,

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