
Erik- thank you very much. The rbinom worked.  

Thanks !
GR





________________________________
From: Erik Iverson-3 [via R] <ml-node+2994186-584049527-199273@n4.nabble.com>

Sent: Wed, October 13, 2010 2:24:18 PM
Subject: Re: Coin Toss Simulation



Shiv wrote: 

> I am trying a simple toin coss simulation, of say 200 coin tosses. The idea 
> is to have a data frame like so: 
>     Experiment#    Number_Of_Heads 
>      1                   104 
>      2                    96 
>      3                    101 
> 
> So I do: 
> 
>  d <-data.frame(exp_num=c(1,2,3));  /* Just 3 experiments to begin with */ 
>  d$head_ct <-sum(sample(0:1,200,repl=TRUE)); 
/* */ is not a valid comment in R, and you don't need ';' either :) 

Just try evaluating the right hand side so that the R interpreter 
prints the result.  This is just calling sample once, and therefore 
you only get one number, 85 in your case. 


>  d; 
>   exp_num    head_ct 
> 1       1        85 
> 2       2        85 
> 3       3        85                             /* the same scalar value is 
> applied to all the rows */ 
> 
> So I tried using "within", and "for", and making the "sum(   " as a 
> function, and I end up with the same...I get the same constant value.  But 
> what I want of course is different "samples".... 
Look at ?replicate or just use ?rbinom directly 

d <-data.frame(exp_num = 1:3) 
d$head_ct <- rbinom(nrow(d), 200, prob = 0.5) 



> 
> 
> 

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