[R] Coin Toss Simulation

[Erik Iverson]

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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