# [R] Integrate and mapply

Vaiva P asvaiva at gmail.com
Sun Nov 7 17:01:30 CET 2010

```Hi,

I need some help on integrating a function that is a vector.
I have a function - vector which each element is different. And,
naturally, function integrate() does not work
I checked the article of U. Ligges and J. Fox (2008) about code
optimization "How Can I Avoid This Loop or Make It Faster?" on
http://promberger.info/files/rnews-vectorvsloops2008.pdf.
Their advice did not help me, because they advised a solution, when
function was the same, but limits of the integral were  vectors. I
have got everything other way around. I could not get any result.
I would be very grateful for an advice on this matter.
The code is below. The function needed to be integrated (undint with
respect to u from 0 to Inf).

Sincerely,
V.

Code

rm=list(ls())

#index matrix
t1<-c(1:15)
t2<-c(1:5)%x%matrix(1,3,1)
t3<-matrix(1,3,1)%x%c(1:5)
t4<-c(1:3)%x%matrix(1,5,1)
comb<-cbind(t1,t2,t3,t4)

nu<-rchisq(15,4)

gam<-matrix(rchisq(75,df=5),15,5)

undint<-function(u){
prob<-function(i) {
i1<-comb[i,1]
i2<-comb[i,2]
i3<-comb[i,3]
i4<-comb[i,4]

val1<-gam[((i3-1)*2+1):(i3*2),i4]
vc1<-matrix(12,length(val1),1)-matrix(u,length(val1),1)-val1
distr1<-prod(pchisq(vc1,df=2))

p10<-distr1*1/(exp(-nu[i1])*(1+gam[i2,i4]))*(1-plogis((u+log(gam[i3,i4])-log(1+gam[i2,i4])),0,1))
p10
}
val<-c(1:15)
q<-sapply(val,prob)
}

```