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. (September 2014)
In this image, the universal set
U (the entire rectangle) is dichotomized into the two sets A (in pink) and its complement Ac
A dichotomy / is a partition of a whole (or a set) into two parts (subsets). In other words, this couple of parts must be
Such a partition is also frequently called a bipartition.
The two parts thus formed are complements. In logic, the partitions are opposites if there exists a proposition such that it holds over one and not the other.
Treating continuous variables or multicategorical variables as binary variables is called dichotomization. The discretization error inherent in dichotomization is temporarily ignored for modeling purposes.
The term dichotomy is from the Greek language Greek: διχοτομία dichotomía "dividing in two" from δίχα dícha "in two, asunder" and τομή tomḗ "a cutting, incision".