LFD Book Forum Question 14 - bias term

#1
06-06-2012, 03:00 PM
 ladybird2012 Member Join Date: Apr 2012 Posts: 32
Question 14 - bias term

For Question 15 we implement the RBF model, and there is a bias term to be calculated. It seems to me that there are two ways of going about this:

1) use a similar logic to what we had for linear regression. This seems to be what is suggested on slide 15 of lecture 16 (RBF network slide).

2) in the RBF notes it's mentioned in the footnote on page 27 that the bias = mean(y).

I implemented both and get different values for the bias as well as for Eout. I was wondering if anyone had tried both methods and come up with consistent values (i.e., I have a bug that I haven't managed to find despite looking hard and long) or if there is a reason to pick one method over the other.

Also while I'm at it, shouldn't the last line of the footnote only refer to w since the centers are chosen in an unsupervised way?
#2
06-06-2012, 03:04 PM
 yaser Caltech Join Date: Aug 2009 Location: Pasadena, California, USA Posts: 1,477
Re: Question 15 - bias term

Quote:
 Originally Posted by ladybird2012 For Question 15 we implement the RBF model, and there is a bias term to be calculated. It seems to me that there are two ways of going about this: 1) use a similar logic to what we had for linear regression. This seems to be what is suggested on slide 15 of lecture 16 (RBF network slide).
This is the correct way. Treat as you treated in linear regression. The only reason it's called here is not to conflict with the SVM kernel version.
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#3
09-05-2012, 02:22 PM
 itooam Senior Member Join Date: Jul 2012 Posts: 100
Re: Question 15 - bias term

TTT (To The Top) Useful to know
#4
09-17-2012, 02:51 AM
 DavidNJ Member Join Date: Jul 2012 Posts: 28
Re: Question 15 - bias term

What is the bias term in a linear regression? Aren't they solved as the pseudo inverse: inv(x'*x)*x'*y?
#5
09-17-2012, 08:39 AM
 yaser Caltech Join Date: Aug 2009 Location: Pasadena, California, USA Posts: 1,477
Re: Question 15 - bias term

Quote:
 Originally Posted by DavidNJ What is the bias term in a linear regression? Aren't they solved as the pseudo inverse: inv(x'*x)*x'*y?
It is in our notation, corresponding to which is the first column of the matrix that is used in the pseudo-inverse.
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