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Removed parenthetical notation implying that "less predictable" and "more complex" are equivalent with respect to data sets describing measurements of processes. This is a highly contentious point within dynamical systems theory, and the comparison isn't doing any important work in the article, so it is better to simply not mention the issue. - RealityApologist (talk) 04:12, 11 January 2013 (UTC)
The algorithm from this article is different than the one cited (http://physionet.org/physiotools/ApEn/) but also different than one of Pincus' article (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC51218/?page=3). I suspect the physionet one is the correct version.