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Old 05-24-2013, 05:31 PM
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yaser yaser is offline
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Join Date: Aug 2009
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Default Re: computing w, b for soft margin SVM

Quote:
Originally Posted by Katie C. View Post
When we compute w from the alphas for the soft-margin SVM which values of alpha do we include? only margin support vectors ( those with 0 < alpha_n < C)? or do we include all of them (0 < alpha_n <= C)?

Similarly, when computing b, can we use any support vector? or only margin support vectors?
1. All of them for computing {\bf w}, since any vector with \alpha>0 will contribute to the derived solution for {\bf w}.

2. Only margin SV's for computing b, since we need an equation, not an inequality, to solve for b after knowing {\bf w}.
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