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Products of Zero-One Matrices

Published online by Cambridge University Press:  20 November 2018

John B. Kelly*
Affiliation:
Arizona State University, Tempe, Arizona
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Let P be a finite set with p objects oj, j = 1, 2, … , p, and let {Si}, i = 1, 2, … , n, be a family of n subsets of P. The incidence matrix A = (aij) for the family {Si} is defined by the rules: aij = 1 if 0j, ∈ Si and aij = 0 if 0jSi. Then, if AAT = B = (bij) (where AT denotes the transpose of A), it is easy to see that bij = |SiSj|, i = 1, … , n, j = 1, … , n, so that the elements of B are integers with biibij ⩾ 0.

Type
Research Article
Copyright
Copyright © Canadian Mathematical Society 1968

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