A REMARK ON ALGORITHM-643 - FEXACT - AN ALGORITHM FOR PERFORMING FISHERS EXACT TEST IN R X C CONTINGENCY-TABLES

The network algorithm of Mehta and Patel [1986] is currently the best general algorithm for computing exact probabilities in r x c contingency tables with fixed marginals. Given here are some improvements to the network algorithm which speed its computational performance; and thus increases the size of problems which can be handled. The new code also eliminates some programming restrictions in the old code, implements the ''hybrid'' algorithm of Mehta and Patel [1986a], and demonstrates that the exact path length bounds of Joe [1988] should always be used in place of the approximate bounds of Mehta and Patel [1986]. The new code can be much faster than the old code in some problems.