Re: Question in PCA - Differentiating problem


In article <dj50i3$9dd2@xxxxxxxxxxxxxxxxxxxxxxxx>,
"Gol Yass" <gol_e_yass@xxxxxxxxx> writes:
>Dear All
>
>I am studying the PCA method , to reduce data dimensions.
>
>I am facing a problem with differentiating the below term to find the
>optimal coefficient ai (where i = 1 to M).
>
>the equation is:
>(x-m-sumof(aiei))^2 = 0
>
>
>Could you recommend recourses or offer a solution ?
>I really don't know how to differentiate series (sumof) !!
>
don't know why you square the zero, maybe you forgot some more
outer summation, but a sum of squares zero means every term zero,
not occuring in PCA
anyway
(d/d ai) (x-m-sum(ai*ei))^2 =
2*(x-m-sum(ai*ei))*ei
chain rule/linearity of differentiation operator
hth
peter

.

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