# chull

0th

Percentile

##### 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 and y, a 2-column matrix x, a list x with two components, etc, see xy.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, 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
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)