R help - Nov 2012 - Counting the numbers of items in vector according to their size

I am new to R and learned to program 10 years ago in C++. I am currently
working a project that looks at the distribution of randomly generated beta
values. I take 20 random beta values find their sum, repeat 100000 times.

Here is my code that it took me 4 hours to get

s=numeric(length=100000)
for(i in 1:100000){
  pop=(rbeta(n=20,shape1=2,shape2=1))
  s[i]=sum(pop)
}

So now I have them all in in vector, I would like to maybe sort or count
them to see how many are less than or equal to 10, but am guessing there is
a density r function that may be easier then that. 



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Hello,

As you know R better it will take you less and less time to get it 
right, and almost surely less and less lines of code to do the same 
thing. Here's a one liner:


set.seed(1510)
s=numeric(length=100000)
for(i in 1:100000){
   pop=(rbeta(n=20,shape1=2,shape2=1))
   s[i]=sum(pop)
}

set.seed(1510)
s2 <- replicate(1e5, {sum(rbeta(n=20,shape1=2,shape2=1))})

identical(s, s2)  # TRUE

As for your question,

hist(s, breaks="Scott")  # Looks normal to me

You can use asymptotic normal theory.

Hope this helps,

Rui Barradas


Em 09-11-2012 17:57, rlcorp escreveu:
> I am new to R and learned to program 10 years ago in C++. I am currently
> working a project that looks at the distribution of randomly generated beta
> values. I take 20 random beta values find their sum, repeat 100000 times.
>
> Here is my code that it took me 4 hours to get
>
> s=numeric(length=100000)
> for(i in 1:100000){
>    pop=(rbeta(n=20,shape1=2,shape2=1))
>    s[i]=sum(pop)
> }
>
> So now I have them all in in vector, I would like to maybe sort or count
> them to see how many are less than or equal to 10, but am guessing there is
> a density r function that may be easier then that.
>
>
>
> --
> View this message in context:
http://r.789695.n4.nabble.com/Counting-the-numbers-of-items-in-vector-according-to-their-size-tp4649085.html
> Sent from the R help mailing list archive at Nabble.com.
>
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