Message-ID: <3EBA826E.4030204@pdf.com>
Date: 2003-05-08T16:14:38Z
From: Spencer Graves
Subject: function to compute entropy
Have you considered:
entropy<-sum(A*logb(A, 2))
hth. spencer graves
Kosenkov Kirill wrote:
> Maybe its slightly off-topic, but can anybody
> help with computing entropy on matrix of probabilities?
>
> Guess we have a matrix of probabilites, A, 2x2, something
> like this:
> z
> x 0 1 2 3 4
> 0 0.063 0.018 0.019 0.016 0.000
> 1 0.011 0.162 0.040 0.042 0.003
> 2 0.015 0.030 0.164 0.033 0.002
> 3 0.012 0.035 0.036 0.159 0.002
> 4 0.004 0.021 0.018 0.013 0.082
>
> sum(A)=1
>
> Can i compute entropy like this:
> entropy<-sum(A*log2(A)) ?
>
> is there a function for computing entropy in R?
>
> Thanx.
>
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