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Nat (unit)

Unit of information

The natural unit of information (symbol: nat), sometimes also **nit ** or nepit, is a unit of information or information entropy, based on natural logarithms and powers of e, rather than the powers of 2 and base 2 logarithms, which define the shannon. This unit is also known by its unit symbol, the nat. One nat is the information content of an event when the probability of that event occurring is 1/e.

One nat is equal to shannons ≈ 1.44 Sh or, equivalently, hartleys ≈ 0.434 Hart.

History

Boulton and Wallace 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.

Alan Turing used the natural ban.

Entropy

Shannon entropy (information entropy), being the expected value of the information of an event, is inherently a quantity of the same type and with a unit of information. The International System of Units, by assigning the same unit (joule per kelvin) both to heat capacity and to thermodynamic entropy implicitly treats information entropy as a quantity of dimension one, with . Systems of natural units that normalize the Boltzmann constant to 1 are effectively measuring thermodynamic entropy with the nat as unit.

When the Shannon entropy is written using a natural logarithm, \Eta = - \sum_i p_i \ln p_i it is implicitly giving a number measured in nats.

Notes

References

Info: Wikipedia Source

This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page.

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