chull
Compute Convex Hull of a Set of Points
Computes the subset of points which lie on the convex hull of the set of points specified.
 Keywords
 graphs
Usage
chull(x, y = NULL)
Arguments
 x, y
 coordinate vectors of points. This can be specified as two
vectors
x
andy
, a 2column matrixx
, a listx
with two components, etc, seexy.coords
.
Details
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).
Value

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.)
References
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
Eddy, W. F. (1977) A new convex hull algorithm for planar sets. ACM Transactions on Mathematical Software, 3, 398403.
Eddy, W. F. (1977) Algorithm 523. CONVEX, A new convex hull algorithm for planar sets[Z]. ACM Transactions on Mathematical Software, 3, 411412.
See Also
Examples
library(grDevices)
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)