Everything about Shannon Entropy totally explained
In
information theory, the
Shannon entropy or
information entropy is a measure of the uncertainty associated with a
random variable. It quantifies the information contained in a message, usually in bits or bits/symbol. It is the minimum message length necessary to communicate information.
This also represents an absolute limit on the best possible lossless
compression of any communication: treating a message as a series of symbols, the shortest possible representation to transmit the message is the Shannon entropy in bits/symbol multiplied by the number of symbols in the original message.
A
fair coin has an entropy of one bit. However, if the coin isn't fair, then the uncertainty is lower (if asked to bet on the next outcome, we'd bet preferentially on the most frequent result), and thus the Shannon entropy is lower. A long string of repeating characters has an entropy of 0, since every character is predictable. The entropy of English text is between 1.0 and 1.5 bits per letter, or as low as 0.6 to 1.3 bits per letter, according to estimates by Shannon based on human experiments.
Equivalently, the Shannon entropy is a measure of the average
information content the recipient is
missing when he does
not know the value of the random variable.
The concept was introduced by
Claude E. Shannon in his 1948 paper "
A Mathematical Theory of Communication".
Definition
The information entropy of a
discrete random variable X, that can take on possible values ,dx.
The relative entropy carries over directly from discrete to continuous distributions, and is invariant under co-ordinate reparametrisations.
Further Information
Get more info on 'Shannon Entropy'.
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