12.07.2015 Views

Entropy and Mutual Information

Entropy and Mutual Information

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<strong>Information</strong> InequalityLet p(x), q(x) be two probability functions definedfor r<strong>and</strong>om variable X, thenD(p||q) ≥ 0.To prove, let A be the support set of p(x). Then−D(p||q) = − ∑ x∈A≤ log( ∑ x∈Ap(x) log p(x)q(x) = ∑ x∈Ap(x) q(x)p(x) ) = log(∑ x∈A≤ log( ∑ x∈Xq(x)) = log 1 = 0.p(x) log q(x)p(x)q(x))<strong>Entropy</strong> <strong>and</strong> <strong>Mutual</strong> <strong>Information</strong> – p. 18

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