Integration in R
On 02-10-2012, at 20:01, Rui Barradas <ruipbarradas at sapo.pt> wrote:
Hello,
Yes, it's possible to remove the loop. Since the loop is used to compute a running product and all we want is the final result, use the vectorized behavior of R and a final ?prod().
Seedup: another 2x. And 4x2 == 8 == 1 [decimal] order of magnitude.
lf2 <-function (x) {
v<-1
x1 <- x[1]
x2 <- x[2]
x3 <- x[3]
x4 <- x[4]
z1 <- exp(x1+x2*dose)
z2 <- exp(x3+x4*dose)
psi0<-1/((1+z1)*(1+z2))
psi1<-z1*psi0
v <- (psi0^y0)*(psi1^y1)*((1-psi0-psi1)^y2)
return( prod(v) )
}
lf2.c <- cmpfun(lf2)
Hope this helps,
Wonderful. It certainly does help. A single nitpick: the v <- 1 at the start of the function can now be removed. I got a speedup of 7.5 compared to the very first version lf1. Berend