[R] Simple simulations

[Steven Kennedy]

#sampling elements
x<-c(rep(0, 20), seq(1:37))

#number of simulations to perform
sims<-100

#vector to store results
results<-c()

#using for loop to perform simulations
for(i in 1:sims){
	#take your sample
	y<-sample(x,3,replace=FALSE)
	#check if all elements are zero
	if(y[1]==0 && y[2]==0 && y[3]==0){
		#return 1 if they are
		results[i]<-1
	} else {
		#otherwise return 0
		results[i]<-0
	}
}

#proportion of simulations where all are zero
sum(results)/sims



On Tue, Jun 28, 2011 at 7:08 AM, robcinm <robcinm at gmail.com> wrote:
> I am taking a basic statistics course this summer, and while the majority of
> the class is using a statistical package that came with the book, I am doing
> everything in R for practical reasons. Forgive me if there is
> documentation/instruction easily available on this topic, but Google and
> forums searches left me with nothing.
>
> We are learning about randomness at the moment and are required to create
> simulations to use as an example. For the problem in the text, there are 57
> numbers with 1 through 20 belonging to the same “group”, meaning the
> probability that a number in that group is picked is 20/57, and 21 through
> 57 are individuals, belonging to no larger group. The point of the exercise
> is to simulate the probability of 1 through 20 being chosen at random (with
> no replacement) three times in a row through hundreds of trials. This is the
> basic syntax I have been using…
>
> sample(c(rep(0, 20), seq(1:37)), 3, replace = F)
>
> That works just fine, but I am wondering if there is a more efficient way of
> doing this. Right now, I am hitting the up arrow and hitting “enter”
> hundreds of times and making note of each time a trial results in 0,0,0. If
> I place this syntax in a rep function, it just repeats the same output of a
> single sample x times instead of giving me new data.
>
>
> --
> View this message in context: http://r.789695.n4.nabble.com/Simple-simulations-tp3628863p3628863.html
> Sent from the R help mailing list archive at Nabble.com.
>
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