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      1 # Entropy
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      3 Ch 6
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      5 **Definition:** Entropy is the average number of bits communicated by one message if message hoarding is allowed.
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      7 Entropy of a finite set of messages is denoted as H(X).
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      9 Formula:
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     11 $H(X) = -\sum_{x\in S} P(x)log_2(P(x))$
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     13 X is an ordered pair (S,P) where S is a finite set of messages and P is a function from S -> [0,1] S.T. P(x) = Probability of x for all x in S.