Zhen Pang wrote:
I also use optim, however, for my case, can you show some light on avoiding the loop?
There are around 200 sets of (i,j,k) where i<=j<=k. 3 situations exist whether "=" hold, I list one for example,
l<-i:(k-j+i) s<-rep(0,k) s[l]<-choose(j,i)*choose((k-j),(l-i))/choose(k,l) ss<-sum(s*x0)
then sum all the log(ss) is my log-liklihood function.
One loop from 1 to 200 is inevitable. I have tried to use vector, however, I only can simply to this situation. Thanks.
Regards,
Zhen
Zhen,
Your question doesn't really have much to do with optim, so I changed the subject line.
It's difficult to see what you're trying to accomplish without a complete example. Could you post one? Also, for loops are necessarily bad.
One thing to note is that you're better off using lchoose in the above code. I.e.
log.s <- lchoose(j, i) + lchoose(k - j, l - i) - lchoose(k, l) s[l] <- exp(log.s)
--sundar
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