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Homework Help: Shannon's :calculating simple uncertainty

  1. Dec 18, 2007 #1
    1. The problem statement, all variables and given/known data

    If I were to use a two-tone image e.g. fax, and were to transmit it line-by-line, where the the individual pixels which make up the line were independent of each other, how would I measure the uncertainty at the transmitter? Also what would the length of the the transmited sequence be if the image was a square NxN image?

    3. The attempt at a solution

    I think the uncertainty is H(X)= - W{ Pilog(Pi) } -B{Qj log (Qj)}
    W=number of white pixels in the sequence
    Pi=probability of a white pixel.
    B=number of black pixels in seqence
    Qj=probability of a black pixel.

    Any ideas would be very helpful...thank you in advance!
  2. jcsd
  3. Dec 18, 2007 #2


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    How did you come up with the formula "H(X)= - W{ Pilog(Pi) } -B{Qj log (Qj)}"?
  4. Dec 18, 2007 #3
    re: shannon's uncertainty

    well the general formula of shannon's uncertainty is:

    H(x)= -pi log(base 2) pi summed over all i, since I have 2 outcomes i.e a black or white pixel i have used Pi=probab. of white and Qj=probab. of black

    also sorry about the cross-posting, it wont happen again.
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