Use this if you are using igraph from R
| convex_hull {igraph} | R Documentation | 
Calculate the convex hull of a set of points, i.e. the covering polygon that has the smallest area.
convex_hull(data)
data | 
 The data points, a numeric matrix with two columns.  | 
A named list with components:
resverts | 
 The indices of the input vertices that constritute the convex hull.  | 
rescoords | 
 The coordinates of the corners of the convex hull.  | 
Tamas Nepusz ntamas@gmail.com
Thomas H. Cormen, Charles E. Leiserson, Ronald L. Rivest, and Clifford Stein. Introduction to Algorithms, Second Edition. MIT Press and McGraw-Hill, 2001. ISBN 0262032937. Pages 949-955 of section 33.3: Finding the convex hull.
M <- cbind( runif(100), runif(100) )
convex_hull(M)