Thread: Exercise 3.4
View Single Post
Old 10-07-2013, 12:00 AM
Sweater Monkey Sweater Monkey is offline
Junior Member
Join Date: Sep 2013
Posts: 6
Default Re: Exercise 3.4

I'm not sure if I'm going about part (e) correctly.

I'm under the impression that E_{\text{test}}(\mathbf{w}_{\text{lin}})=\frac{1}{N}||X{\mathbf{w}}_{lin}-\mathbf{y'}||^2

where \hat{\mathbf{y}}=X{\mathbf{w}}_{lin}=X\mathbf{w}^*+H\mathbf{\epsilon} as derived earlier
and \mathbf{y'}=\mathbf{w}^{*T}\mathbf{x}+\mathbf{\epsilon'}=X\mathbf{w}^*+\mathbf{\epsilon'}

This lead me to \frac{1}{N}||H\mathbf{\epsilon}-\mathbf{\epsilon'}||^2

I carried out the expansion of this expression and then simplified into the relevant terms but my final answer is \sigma^2(1+(d+1)) because the N term cancels out.

Am I starting out correctly up until this expansion or is my thought process off from the start? And if I am heading in the right direction is there any obvious reason that I may be expanding the expression incorrectly? Any help would be greatly appreciated.
Reply With Quote