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From: shahnaz fatima on 11 Aug 2010 10:52
if anybody can refer to my earlier posts in which i have put a function on lda,
MY DOBUT IS IN THIS FORMULA,ACCORDING TO THEORY,
> > sb=sb+nums(i)*(means(i,:)-allmean)'*(means(i,:)-allmean);
> >
> > nums(i) such term is not there in formula of lda;. i dont understand why this nums term.
> >
> > if anybody can plz help me , i shall be thankful. plz
From: Greg Heath on 12 Aug 2010 19:36
On Aug 11, 10:52 am, "shahnaz fatima" <shahnaz1981...(a)gmail.com>
wrote:
> if anybody can refer to my earlier posts in which i have put a function on lda,
> MY DOBUT IS IN THIS FORMULA,ACCORDING TO THEORY,
>
>
>
> > >  sb=sb+nums(i)*(means(i,:)-allmean)'*(means(i,:)-allmean);  
>
> > > nums(i) such term is not there in formula of lda;. i dont understand why this nums term.
>
> > > if anybody can plz help me , i shall be thankful.

I think if you start with the between class double sum class mean
difference
form

Sb = sum(i=1,c){sum(j=1,c){(Mi-Mj)'*(Mi-Mj)}}

and use the global mean identity

M0 = (Ni*Mi+Nj*Mj)/(Ni+Nj)

you can obtain the single sum form

Sb = sum(i=1,c){ (Mi-M0)' * (Mi-M0) }

Hope this helps.

Greg


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