#1




Question 11
I have used LIBSVM; the answer that I get is one of a) to d) if I scale it appropriately. However, if I scale it, the margin in the transformed domain is not any more +/1 at the support vectors. So technically the answer proposed is right (since it separates the points with a maximum margin) but it doesn't satisfy the requirement that the margins be +/ 1 at the support vectors.

#2




Re: Question 12
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#3




Re: Question 12
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Thanks, Fernando. 
#4




Re: Question 12
LIBSVM is getting popular . Someone even applied it to the puzzle from Lecture 1 if you remember that.
http://book.caltech.edu/bookforum/sh...21&postcount=6
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#5




Re: Question 12
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#6




Re: Question 12
Geometrically, it is clear to see what the values of the weights and b should be. My results using a geometric approach match the results I get using Octave implemenation of SVM. Of course, libsvm also confirms my results as it always has the final say in matters related to SVM .

#7




Re: Question 12
It seems like the original question was never answered.
Geometrically, one can find a w1, w2, and b which define the separating plane. Clearly you get the same plane if you multiply w1, w2, and b by some constant A. In the SVM formalism A was fixed so that w.z+b=1 at the nearest positive point. Do we need to choose the w1, w2, and b which define the correct plane AND have the correct A, or is it sufficient to choose one of the infinitely many w1, w2, and b which define the correct plane without necessarily having the correct normalization A? It's also possible that the correct answer has the correct normalization and I've made some mistake. 
#8




Re: Question 12
Quote:
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#9




Re: Question 12
Great  looking back I agree that the question wording is unambiguous, though perhaps for this problem the graph of P(getting the right answer) vs Carefulness is nonmonotonic. Thank you!

#10




Re: Question 12
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