title: Neural network octave implementation
body: <p>Can anyone explain me this:</p>
  
  <pre><code>Theta1_grad(:, 1) = Theta1_grad(:, 1) ./ m;
  
  Theta1_grad(:, 2:end) = Theta1_grad(:, 2:end) ./ m + ((lambda/m) * Theta1(:, 2:end));
  </code></pre>
  
  <p>I'm implementing in python, and I don't know Octave, I just found this neural network implementation, but I don't understand what is this doing.</p>
  
  <p>Reference: <a href="http://feature-space.com/en/document49.pdf" rel="nofollow">http://feature-space.com/en/document49.pdf</a> - 
  Page 12 (2.5)</p>
  
  <h2>EDIT:</h2>
  
  <p>Never mind, I think its trying to not to modify 1st column.</p>