[R] automated integration?

francogrex francogrex at mail.com
Tue Jan 23 13:57:05 CET 2007

```When I run the script below it works well it ouputs the result that I need,
in this case were n=45 and e=5.02689 the result is: 6.669578
-----------------------------------------------
dens<-function(x){
n=45
e=5.02689
a1=0.0987
b1=0.04261
a2=1.043
b2=1.222
p=0.121
if (n>200)  c((n=n/2),(e=e/2))
if (e>30)  c((n=n/2),(e=e/2))
lpp<-((lgamma(a1+n)))-(lgamma(a1)+lfactorial(n)+log((1+(e/b1))^a1)+log((1+(b1/e))^n))
lzz<-((lgamma(a2+n)))-(lgamma(a2)+lfactorial(n)+log((1+(e/b2))^a2)+log((1+(b2/e))^n))
pp<-exp(lpp)
zz<-exp(lzz)
qq= (p*pp)/((p*pp)+((1-p)*zz))
lgam<-(log((b1+e)^(a1+n)) + log(x^((a1+n)-1)))   - (lgamma((a1+n))   +
((b1+e)*x))
lgom<-(log((b2+e)^(a2+n)) + log(x^((a2+n)-1)))   - (lgamma((a2+n))   +
((b2+e)*x))
gam<-exp(lgam)
gom<-exp(lgom)
(qq*gam)  + ((1-qq)*gom)
}
integ<-function(x){
n=45
e=5.02689
if (x>(n/e)) return (x=Inf)
if (x<0) return (x=0)
u<-integrate(dens,lower=0, upper=x)\$value
u-0.05
}
uni<-uniroot(integ,c(0,100), tol=1e-10)
uni\$root
-----------------------------------------------------------------

But what if n and e are vectors (like: n=c(31,22,47,38) and
e=c(5.2,2.8,3.4,2.1)? can I have a string of results all at once instead of
entering the values of n and e one by one it takes such a long time
especially if the n and e contain a couple of 100 values!

Any suggestions are appreciated. Thanks
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