View Single Post
Old 05-06-2013, 12:37 PM
pyguy pyguy is offline
Junior Member
Join Date: Apr 2013
Posts: 5
Default Q8 implementation question

I'm trying to compute the stochastic gradient descent for linear regression, and the formula I'm using is:

\nabla e_n(\mathbf w) = \frac{-y_n\mathbf x_n}{1 + e^{y_n\mathbf{w^T}\mathbf{x_n}}}

I'm running the experiment with what I believe to be the correct inputs, but I'm not getting the what I expect to be the output, so I'm trying to trace my steps and see where I went wrong. I was looking at the formula, and one part that I was uncertain about was the \mathbf{w^T}\mathbf{x_n} part. Aren't \mathbf{w} and \mathbf{x_n} both 1x3 row vectors? If I transpose \mathbf{w}, and multiply, I'd get a 3x3 matrix which didn't make sense to me in the calculation, so I'm essentially multiplying them right now as if they were just 1x3 row vectors.
Reply With Quote