Hi All,
I am trying to convert the following piece of matlab code to R:
XX1 = sum(w(:,ones(1,N1)).*X1.*X1,1); #square the elements of X1,
weight it and repeat this vector N1 times
XX2 = sum(w(:,ones(1,N2)).*X2.*X2,1); #square the elements of X2,
weigh and repeat this vector N2 times
X1X2 = (w(:,ones(1,N1)).*X1)'*X2; #get the weighted
'covariance' term
XX1T = XX1'; #transpose
z = XX1T(:,ones(1,N2)) + XX2(ones(1,N1),:) - 2*X1X2; #get the
squared weighted distance
which is basically doing: z=(X1-X2)' W (X1-X2)
What would the best way (for SPEED) to do this? or is vectorizing as above
the best? Any hints, suggestions?
Thanks,
Sachin
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