# [R] R function help!

Pete Brecknock Peter.Brecknock at bp.com
Tue Feb 19 00:01:58 CET 2013

```simonj16 wrote
> Consider an urn that contains 10 tickets, labelled: 1,1,1,1,2,5,5,10,10,10
>
> I want to draw with replacement n=40 tickets. I am interested in the sum,
> Y, of the 40 ticket values that I draw
>
> Write an R function named urn.model that simulates this experiement. What
> I have below is not working.
>
> flip.n = function(p,n) {
> 	return(runif(n,0,1) < p)
> }
> ticket.ns<-c(1,1,1,1,2,5,5,10,10,10)
> urn.model = function(ticket.ns) {
> 	draws.per.sim = 1
> 	prob = .1
> 	urn.results = rep(-1, ticket.ns)
> 	for (i in 1:ticket.ns) {
> 		draws = flip.n(prob,draws.per.sim)
> 		num =sum(draws,ticket.ns)
> 		urn.results[i] = num
> 	}
> 	return(urn.results)
> }
> urn.25.samples =urn.model(25)
>
> urn.25.samples
>
>
> Use urn.model to generate a sample y={y1,...,y25) of n=25 observed sums.

Any good?

ticket.ns<-c(1,1,1,1,2,5,5,10,10,10)

draw=NULL
for (i in 1:25){
draw[i] <- sum(sample(ticket.ns,40,replace=TRUE))
}

print(draw)

HTH

Pete

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