preprint · arXiv (Cornell University) · 2011

Extropy: Complementary Dual of Entropy

Lad, Frank, Sanfilippo, Giuseppe, Agrò, Gianna

Cited by 1Open access

Abstract

This article provides a completion to theories of information based on entropy, resolving a longstanding question in its axiomatization as proposed by Shannon and pursued by Jaynes. We show that Shannon's entropy function has a complementary dual function which we call "extropy." The entropy and the extropy of a binary distribution are identical. However, the measure bifurcates into a pair of distinct measures for any quantity that is not merely an event indicator. As with entropy, the maximum extropy distribution is also the uniform distribution, and both measures are invariant with respect to permutations of their mass functions. However, they behave quite differently in their assessments of the refinement of a distribution, the axiom which concerned Shannon and Jaynes. Their duality is specified via the relationship among the entropies and extropies of course and fine partitions. We also analyze the extropy function for densities, showing that relative extropy constitutes a dual to the Kullback-Leibler divergence, widely recognized as the continuous entropy measure. These results are unified within the general structure of Bregman divergences. In this context they identify half the $L_2$ metric as the extropic dual to the entropic directed distance. We describe a statistical application to the scoring of sequential forecast distributions which provoked the discovery.

Cite this paper

APA 7

Lad, F., Sanfilippo, G., & Agrò, G. (2011). Extropy: Complementary Dual of Entropy. arXiv (Cornell University). https://doi.org/10.48550/arxiv.1109.6440

MLA 9

Lad, Frank, et al. “Extropy: Complementary Dual of Entropy.” arXiv (Cornell University), 2011, https://doi.org/10.48550/arxiv.1109.6440.

Chicago

Lad, Frank, Giuseppe Sanfilippo, and Gianna Agrò. 2011. “Extropy: Complementary Dual of Entropy.” arXiv (Cornell University). https://doi.org/10.48550/arxiv.1109.6440.

Harvard

Lad, F., Sanfilippo, G. and Agrò, G. (2011) ‘Extropy: Complementary Dual of Entropy’, arXiv (Cornell University). Available at: https://doi.org/10.48550/arxiv.1109.6440.

BibTeX

@misc{lad2011extropy,
  title = {{Extropy: Complementary Dual of Entropy}},
  author = {Lad, Frank and Sanfilippo, Giuseppe and Agrò, Gianna},
  journal = {arXiv (Cornell University)},
  year = {2011},
  doi = {10.48550/arxiv.1109.6440}
}

Made from the index record. Check names, capitalisation and page numbers against the paper. Need another style? AI for Research has over 10,000.