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Sent from my phone. Please excuse my brevity.
Kathie <kathryn.lord2...@gmail.com> wrote:
Dear R users,
I have two n*1 integer vectors, y1 and y2, where n is very very large.
I'd like to compute
elbp = 4^(y1) * 5^(y2) * sum_{i=0}^{max(y1, y2)} [{ (y1-i)! * (i)! *
(y2-i)! }^(-1)];
that is, I need to compute "elbp" for each (y1, y2) pair.
So I made R code like below, but I don't think it's efficient
Would you plz tell me how to avoid this "for" loop blow??
_____________________________________________
for (k in 1:n){
ymax <- max( y1[k], y2[k] )
i <- 0:ymax
sums<- -lgamma(y1[k]-i+1)-lgamma(i+1)-lgamma(y2[k]-i+1)
maxsums <- max(sums)
sums <- sums - maxsums
lsum <- log( sum(exp(sums)) ) + maxsums
lbp[k] <- y1[k]*log(4) + y2[k]*log(5) + lsum
}
elbp <- exp(lbp)
_____________________________________________
Any suggestion will be greatly appreciated.
Regards,
Kathryn Lord
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