[R] Sample Poisson Distribution

[Abhijit Dasgupta]

Do you mean that you have 100 samples, each of size 1000. If this is so, 
you can perhaps do:

N = 1000
n = 100
x = matrix(rpois(N*n, 3.1), ncol=100) # Generate the appropriate no. of 
Poisson samples and rearrange into 100 columns of 1000

output = cbind(means=apply(x,2,mean), vars=apply(x,2,var)) # 
apply(x,2,mean) runs "mean" on each column of x

What do you want to draw the histograms of? Histograms of the means 
and/or variances can be done by
hist(output$means)
hist(output$vars)

Hope this helps

Abhijit

Thor wrote:
> Hi,
>  I'm completely new to R, I am all at sea with the interface and the
> confusing help files, so would appreciate some help to do a simple task.
>
> Need to present the mean and variance of 100 different samples of poisson
> distributions (N=1000, with fixed lambda) in a file in two columnns, and
> then produce histograms.
>
> So far I have figured out:
>
>   
>> N <- 1000
>>  x <- rpois(N, 3.1) ,
>>     
>
> and 
>   
>> var(x) 
>>     
> and 
>   
>> mean(x)
>>     
> , and I've seen the hist command, just need to tie it all together.  I read
> that loops aren't really used in R, so what do i need to do?
>
> thanks
>