Re: [R] more efficient double summation...

On Fri, 29 Aug 2008, Giovanni Petris wrote: You can cut execution time by a factor 2 simply using the fact that the double summation is symmetric in the indices j and k: 2 * sum(sapply(1:(m-1), function(k){sum(sapply((k-1):m, function(j){x[k]*x[j]*dnorm((mu[j]+mu[k])/sqrt(sig[k]+sig[j]))/sqr

Re: [R] more efficient double summation...

You can cut execution time by a factor 2 simply using the fact that the double summation is symmetric in the indices j and k: 2 * sum(sapply(1:(m-1), function(k){sum(sapply((k-1):m, function(j){x[k]*x[j]*dnorm((mu[j]+mu[k])/sqrt(sig[k]+sig[j]))/sqrt(sig[k]+sig[j])}))})) + sum(x^2*dnorm((2*mu

[R] more efficient double summation...

Dear R users... I made the R-code for this double summation computation http://www.nabble.com/file/p19213599/doublesum.jpg - Here is my code.. sum(sapply(1:m, function(k){sum(sapply(1:m, function(j){x[k]*x[j]*dnorm((mu[j]+mu[k])/sqrt(sig[k]+si