# Probability from log likelihood in LDA output Classic List Threaded 4 messages Open this post in threaded view
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## Probability from log likelihood in LDA output

 Hello, As I understand it, the output for LDA is a log likelihood value for each word/topic pair, which is a function of log(P(w|t)). Is it possible to invert that function to obtain P(w|t)? I have a feeling it is not, since it looks like the final value is obtained as a sum of log probabilities, but I just wanted to check, since an output as a probability is more readable than the likelihood value given. Thanks, Andres
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## Re: Probability from log likelihood in LDA output

 Yes.  I should be possible to use exp to get the actual probability.  The fact that it is a sum of log probabilities just means that the probability is a product of probabilities. It is possible that the probabilities are not normalized, but that would be a bit surprising for this kind of algorithm. On Mon, Dec 6, 2010 at 8:02 AM, Quiroz Hernandez, Andres < [hidden email]> wrote: > Hello, > > As I understand it, the output for LDA is a log likelihood value for > each word/topic pair, which is a function of log(P(w|t)). Is it possible > to invert that function to obtain P(w|t)? I have a feeling it is not, > since it looks like the final value is obtained as a sum of log > probabilities, but I just wanted to check, since an output as a > probability is more readable than the likelihood value given. > > Thanks, > > Andres >