NAT (INFORMATION)

A 'nat' (sometimes also 'nit' or even 'nepit') is a logarithmic unit of information or entropy, based on natural logarithms and powers of ''e'', rather than the powers of 2 and base 2 logarithms which define the bit. The ''nat'' is the natural unit for information entropy, corresponding to Boltzmann's constant for thermodynamic entropy.
When the Shannon entropy is written using a natural logarithm,
:$H\; =\; -\; sum\_i\; p\_i\; ln\; p\_i\; !,$
it is implicitly giving a number measured in ''nats''.
One nat corresponds to about 1.44 bits $left\; (\; frac\{1\}\{ln\; 2\}$
ight ), or 0.434 hartleys $left\; (\; frac\{1\}\{ln\; 10\}$
ight ).

Contents

History

References

History

Alan Turing used the ''natural ban'' (Hodges 1983, ''Alan Turing: The Enigma.''). Boulton and Wallace (1970) used the term ''nit'' in conjunction with minimum message length which was subsequently changed by the minimum description length community to ''nat'' to avoid confusion with the nit used as a unit of luminance (Comley and Dowe, 2005, sec. 11.4.1, p271).

References

★ J.W. Comley and D.L. Dowe, ``Minimum Message Length, MDL and Generalised Bayesian Networks with Asymmetric Languages'', Chapter 11 (pp265-294) in P. Grünwald, I. J. Myung and M. A. Pitt (eds.), `Advances in Minimum Description Length: Theory and Applications', MIT Press (ISBN 0-262-07262-9), April 2005.

★ Fazlollah M. Reza. ''An Introduction to Information Theory''. New York: Dover 1994. ISBN 0486682102