[R] Add transitivity to a matrix?

Duncan Murdoch murdoch@dunc@n @end|ng |rom gm@||@com
Mon Jun 17 19:19:13 CEST 2019

Suppose I have a square logical matrix M which I'm thinking of as a 
relation between the row/column numbers.

I can make it into a symmetric relation (i.e. M[i,j] being TRUE implies 
M[j,i] is TRUE) by the calculation

M <- M | t(M)

Is there a simple way to ensure transitivity, i.e. M[i,j] & M[j,k] both 
being TRUE implies M[i,k] is TRUE?

The operation should only change FALSE or NA values to TRUE values; TRUE 
values should never be changed.

Duncan Murdoch

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