[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
>
> Follow up question:
>
> 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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