[R] R-help

[G. Jay Kerns]

Dear Lemarian,

I was going to reply to say this is how I would do (almost) the same
thing with the prob package:

library(prob)
S <- rolldie(2, makespace = TRUE)
tmp <- sim(S, ntrials = 10000)
with(tmp, mean(X1 == X2))

but then it occurred to me that Greg's "dice" was much faster than
"sim" (plus that graph of the die faces is really cool!) so I was just
going to let it go.  But then again it occurred to me that simulation
isn't needed for the problem at all:

prob(S, X1 == X2)

But finally as a reality-check it occurred to me that for a problem
like this using R is like shooting a squirrel with a ballistic
missile.  Not that there's anything wrong with that;  I don't like
squirrels.

Cheers,
Jay

P.S.  Just kidding.




On Tue, Oct 5, 2010 at 12:06 PM, Greg Snow <Greg.Snow at imail.org> wrote:
> I would do it like this:
>
> library(TeachingDemos)
> tmp <- dice(10000, 2)
> with(tmp, c(sum(Red==Green),mean(Red==Green)) )
> plot(head(tmp,28))
>
>
>
>
> --
> Gregory (Greg) L. Snow Ph.D.
> Statistical Data Center
> Intermountain Healthcare
> greg.snow at imail.org
> 801.408.8111
>
>
>> -----Original Message-----
>> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
>> project.org] On Behalf Of Lemarian WallaceIII
>> Sent: Monday, October 04, 2010 10:14 PM
>> To: r-help at r-project.org
>> Subject: [R] R-help
>>
>> Im trying to simulate the rolling of a pair of dice
>>
>> this is my function:
>> #function to simulate tosses of a pair of dice
>> #from the simulation, the program returns the empirical probability of
>> #observing a double
>> count <- 0
>> for(j in 1:sim){#begin loop
>> die1 <- sample(1:6,1)
>> print(die1)
>> die2 <- sample(1:6,1)
>> print(die2)
>> count <- ifelse(die1 == die2, count + 1, count)
>> }#end loop
>> emprob <- count/sim
>> return(count,emprob)
>> } #end program
>>
>>
>> these are the errors that keep coming up:
>> Error in 1:sim : 'sim' is missing
>>
>>
>> How do I correct this?
>>
>>
>>
>>       [[alternative HTML version deleted]]
>
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>



-- 
***************************************************
G. Jay Kerns, Ph.D.
Associate Professor
Department of Mathematics & Statistics
Youngstown State University
Youngstown, OH 44555-0002 USA
Office: 1035 Cushwa Hall
Phone: (330) 941-3310 Office (voice mail)
-3302 Department
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VoIP: gjkerns at ekiga.net
E-mail: gkerns at ysu.edu
http://people.ysu.edu/~gkerns/