On 11/14/06, Ravi Varadhan <[EMAIL PROTECTED]> wrote:
> I am trying to do the following computation:
>
> p <- rep(0, n)
> coef <- runif(K+1)
> U <- matrix(runif(n*(2*K+1)), n, 2*K+1)
> for (i in 0:K){
> for (j in 0:K){
> p <- p + coef[i+1]* coef[j+1] * U[,i+j+1]
> } }
>
> I would appreciate any suggestions on how to perform this computation
> efficiently without the "for" loops?
This kicks butt on my machine:
p <- as.vector(U %*% convolve(coef,rev(coef),type="open"))
HTH!
Richard Graham
JHU '84 EE&CS
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