`chull(x, y = NULL)`

x, y

coordinate vectors of points. This can be specified as two
vectors

`x`

and `y`

, a 2-column matrix `x`

, a list
`x`

with two components, etc, see `xy.coords`

.-
An integer vector giving the indices of the unique points lying on the
convex hull, in clockwise order. (The first will be returned for
duplicate points.)

`xy.coords`

is used to interpret the specification of the
points. Infinite, missing and `NaN`

values are not allowed.The algorithm is that given by Eddy (1977).

Eddy, W. F. (1977) A new convex hull algorithm for planar sets.
*ACM Transactions on Mathematical Software*, **3**, 398--403.

Eddy, W. F. (1977) Algorithm 523. CONVEX, A new convex hull
algorithm for planar sets[Z]. *ACM Transactions on
Mathematical Software*, **3**, 411--412.

`xy.coords`

, `polygon`

X <- matrix(stats::rnorm(2000), ncol = 2) chull(X) ## Not run: # # Example usage from graphics package # plot(X, cex = 0.5) # hpts <- chull(X) # hpts <- c(hpts, hpts[1]) # lines(X[hpts, ]) # ## End(Not run)