chull {grDevices} | R Documentation |
Computes the subset of points which lie on the convex hull of the set of points specified.
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 . |
xy.coords
is used to interpret the
specification of the points. The algorithm is that given by Eddy (1977).
‘Peeling’ as used in the S function chull
can be
implemented by calling chull
recursively.
An integer vector giving the indices of the points lying on the convex hull, in clockwise order.
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, 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.
X <- matrix(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)