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rohanag 05-07-2012 02:43 AM

clarification on lecture 9
 
I have a slight problem with delta_E_in in slide 23 of lecture 9.

https://public.sn2.livefilestore.com...led.png?psid=1

I think there should be a negative sign in the exponentiation term,
e^(y_n * w.transpose * x_n) should be e^( - y_n * w.transpose * x_n )

as it would result from differentiating the cross entropy error? Please clarify.

https://public.sn2.livefilestore.com...cte.png?psid=1

Thank you

IamMrBB 05-07-2012 03:13 AM

Re: clarification on lecture 9
 
The formula on the slide is correct.

d/dx (ln(1+exp(-f(x))) = -exp(-f(x))f'(x)/(1+exp(-f(x))

now multiply both numerator and denominator with exp(f(x)) and the right formula -f'(x)/(exp(f(x))+1) follows since exp(f(x))*exp(-f(x)) = 1

rohanag 05-07-2012 03:33 AM

Re: clarification on lecture 9
 
got it, thanks


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