R help - Oct 2012 - simulating a toss of a coin

All,

I've devised a way to toss a coin three times and record the number of
heads, then use the table command to summarize the number of time 0, 1, 2, or 3
heads were obtained.

n <- 100
x <- sample(c("H","T"),3*n,replace=TRUE)
dim(x) <- c(3,n)
num_heads <- apply(x,2,function(x) sum(x=="H"))
table(num_heads)/n

What I'd like to do next is run this code 10 times, and gather the results
in a matrix with 10 rows and 4 columns, where the first row records the output
of the first run of the above code, the second row records the second run of the
above code, etc.

Looking for some simple ideas on how to accomplish this.

Thanks.

David

On Tue, Oct 9, 2012 at 6:04 AM, David Arnold <dwarnold45 at
suddenlink.net> wrote:
> All,
>
> I've devised a way to toss a coin three times and record the number of
heads, then use the table command to summarize the number of time 0, 1, 2, or 3
heads were obtained.
>
> n <- 100
> x <- sample(c("H","T"),3*n,replace=TRUE)
> dim(x) <- c(3,n)
> num_heads <- apply(x,2,function(x) sum(x=="H"))
> table(num_heads)/n
>
> What I'd like to do next is run this code 10 times, and gather the
results in a matrix with 10 rows and 4 columns, where the first row records the
output of the first run of the above code, the second row records the second run
of the above code, etc.
>
> Looking for some simple ideas on how to accomplish this.
>
> Thanks.
>
> David
Hi David,

This is that wonderful smell of homework in the morning, so I can't
really say too much in good conscience, but I think you are looking
for

?replicate

Cheers,
Michael

Hello,

Try the following.


fun <- function(n = 100){
     x <- sample(c("H","T"),3*n,replace=TRUE)
     dim(x) <- c(3,n)
     num_heads <- apply(x,2,function(x) sum(x=="H"))
     table(num_heads)/n
}

Runs <- 1e1
t(replicate(Runs, fun()))

Hope this helps,

Rui Barradas
Em 09-10-2012 06:04, David Arnold escreveu:
> All,
>
> I've devised a way to toss a coin three times and record the number of
heads, then use the table command to summarize the number of time 0, 1, 2, or 3
heads were obtained.
>
> n <- 100
> x <- sample(c("H","T"),3*n,replace=TRUE)
> dim(x) <- c(3,n)
> num_heads <- apply(x,2,function(x) sum(x=="H"))
> table(num_heads)/n
>
> What I'd like to do next is run this code 10 times, and gather the
results in a matrix with 10 rows and 4 columns, where the first row records the
output of the first run of the above code, the second row records the second run
of the above code, etc.
>
> Looking for some simple ideas on how to accomplish this.
>
> Thanks.
>
> David
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