[R] Integration in R
Berend Hasselman
bhh at xs4all.nl
Tue Oct 2 20:18:49 CEST 2012
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
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