[R] ordering points as vertex of a polygon

[Luca Scrucca]

Dear R-users,

Suppose I have the following x-y coordinates which give the boundaries of
a polygon:
> x <- c(5,4,5,9,6,6,4,7,10,7,10,4,10)
> y <- c(6,3,2,6,3,7,5,4,4,7, 5,4, 6)

I would like to plot the following graph:
> plot(x,y)
> ord <- c(7,12,2,3,5,8,9,11,13,4,10,6,1)
> polygon(x[ord],y[ord])

How I can obtain the above ordering (in the example an anti-clockwise
ordering) such that I can use polygon() to connect the points?

I searched previous messages but I did not find any relevant to this
problem.

Thanks,

Luca

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| Dr. Luca Scrucca                                                      |
| Dipartimento di Scienze Statistiche      tel. +39 - 075 - 5855278     |
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