[R] What don't I understand about sample()?

[Bert Gunter]

Bravo for your unrequired R efforts.

You misunderstand the nested call. sample() is called only once,
producing 1 sample of 10 with replacement. Since your matrix call
needs 50 values, ?matrix tells you (in details):
"If there are too few elements in data to fill the matrix, then the
elements in data are recycled. If data has length zero, NA of an
appropriate type is used for atomic vectors (0 for raw vectors) and
NULL for lists.

This sort of "recycling" is quite standard in R. Though not universal.

Cheers,
Bert

"An educated person is one who can entertain new ideas, entertain
others, and entertain herself."

On Thu, Mar 13, 2025 at 2:23 PM Kevin Zembower via R-help
<r-help using r-project.org> wrote:
>
> Hello, all,
>
> I'm learning to do randomized distributions in my Stats 101 class*. I
> thought I could do it with a call to sample() inside a matrix(), like:
>
> > matrix(sample(1:10, replace=TRUE), 5, 10, byrow=TRUE)
>      [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
> [1,]    8    2    3    1    8    2    8    8    9     8
> [2,]    8    2    3    1    8    2    8    8    9     8
> [3,]    8    2    3    1    8    2    8    8    9     8
> [4,]    8    2    3    1    8    2    8    8    9     8
> [5,]    8    2    3    1    8    2    8    8    9     8
> >
>
> Imagine my surprise to learn that all the rows were the same
> permutation. I thought each time sample() was called inside the matrix,
> it would generate a different permutation.
>
> I modeled this after the bootstrap sample techniques in
> https://pages.stat.wisc.edu/~larget/stat302/chap3.pdf. I don't
> understand why it works in bootstrap samples (with replace=TRUE), but
> not in randomized distributions (with replace=FALSE).
>
> Thanks for any insight you can share with me, and any suggestions for
> getting rows in a matrix with different permutations.
>
> -Kevin
>
> *No, this isn't a homework problem. We're using Lock5 as the text in
> class, along with its StatKey web application. I'm just trying to get
> more out of the class by also solving our problems using R, for which
> I'm not receiving any class credit.
>
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