Naive Bayes Confusion;
<p>I'm working on homework for my machine learning course and am having trouble understanding the question on Naive Bayes. The problem I have is a variation of question number 2 on the following page:</p>

<p><a href="https://www.cs.utexas.edu/~mooney/cs343/hw3-old/hw3.html" rel="nofollow noreferrer">https://www.cs.utexas.edu/~mooney/cs343/hw3-old/hw3.html</a></p>

<p>The numbers I have are slightly different, so I'll replace the numbers from my assignment with the example above. I'm currently attempting to figure out the probability that the first text is physics. To do so, I have something that looks a little like this:</p>

<p>P(physics|c) = P(physics) * P(carbon|physics) * p(atom|physics) * p(life|physics) * p(earth|physics) / [SOMETHING]</p>

<p>P(physics|c) = .35 * .005 * .1 * .001 * .005 / [SOMETHING]</p>

<p>I'm basing this off of an example that I've seen in my notes, but I can't seem to figure out what I'm supposed to divide by. I'll provide the example from the notes as well.</p>

<p><img src="https://i.imgur.com/erI5Bq0.png" alt="example from notes"></p>

<p>Perhaps I'm going about this in the wrong way, but I'm unsure where the P(X) term that we're dividing by is coming from. How does this relate to the probability that the text is physics? I feel that getting this issue resolved will make the remainder of the assignment simple.</p>