R help - Apr 2011 - Repeating a function

Hello all,

I currently have this function:

drift <-function(p0=0.4,N=40,ngen=55){
	p = p0
	for( i in 1:ngen){
		p = rbinom(1,2*N,p)/(2*N)
		}
	return( p )
	}

I want to repeat it 1000 times, then do some analysis on the results. I've
tried using the rep() function, but that only gives me repeats of the first
value of p. How can I get 1000 values of p for different iterations of the
function?

Thanks in advance

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Hi,

try this;

output <- list()

times <- 1000

drift <-function(p0=0.4,N=40,ngen=55){
        p = p0
        for( i in 1:ngen){
                p = rbinom(1,2*N,p)/(2*N)
                }
        return( p )
        } 
for(i in 1:times){
result <- drift(0.4, 40, 55)

output <- c(output, list(result))
}

Then, you can use the "output" with unlist() to do analysis. For
example
mean(unlist(output))

Helin.

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Hi:

The r<dist> functions are vectorized, so the loop is unnecessary:

drift <- rbinom(55, 80, 0.4)

or within a function,

drift <- function(p0 = 0.4, N = 40, ngen = 55) rbinom(ngen, 2 * N, p0)

To repeat it 1000 times, you have at least two options:

(1)   [1000 columns]
simmat <- replicate(1000, drift())

(2)  [1000 rows]
simmat <- matrix(drift(0.4, 40, 1000 * 55), nrow = 1000)

HTH,
Dennis

On Sun, Apr 17, 2011 at 4:48 PM, Sclera <kn0wzal0t at gmail.com>
wrote:
> Hello all,
>
> I currently have this function:
>
> drift <-function(p0=0.4,N=40,ngen=55){
> ? ? ? ?p = p0
> ? ? ? ?for( i in 1:ngen){
> ? ? ? ? ? ? ? ?p = rbinom(1,2*N,p)/(2*N)
> ? ? ? ? ? ? ? ?}
> ? ? ? ?return( p )
> ? ? ? ?}
>
> I want to repeat it 1000 times, then do some analysis on the results.
I've
> tried using the rep() function, but that only gives me repeats of the first
> value of p. How can I get 1000 values of p for different iterations of the
> function?
>
> Thanks in advance
>
> --
> View this message in context:
http://r.789695.n4.nabble.com/Repeating-a-function-tp3456295p3456295.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org mailing list
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> PLEASE do read the posting guide
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>