[R] getting all circular arrangements without accounting for order
maitra at email.com
Fri Mar 30 05:10:05 CEST 2018
Yes, however, this seems a bit wasteful. Just wondering if there are other, more efficient options possible.
On Thu, 29 Mar 2018 22:20:19 -0400 Boris Steipe <boris.steipe at utoronto.ca> wrote:
> If one is equal to the reverse of another, keep only one of the pair.
> > On Mar 29, 2018, at 9:48 PM, Ranjan Maitra <maitra at email.com> wrote:
> > Dear friends,
> > I would like to get all possible arrangements of n objects listed 1:n on a circle.
> > Now this is easy to do in R. Keep the last spot fixed at n and fill in the rest using permuations(n-1, n-1) from the gtools package.
> > However, what if clockwise or counterclockwise arrangements are the same? I know that half of the above (n - 1)! arrangements are redundant.
> > Is there an easy way to list these (n-1)!/2 arrangements?
> > I thought of only listing the first half from a call to permuations(n - 1, n - 1), but while this holds for n = 4, it does not for n = 5. So, I am wondering if there is another function or tweak which would easily do this.
> > Many thanks in advance for any help. and best wishes,
> > Ranjan
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