Identifying elements of an array in clockwise order

If I have an array A such that it contains vertex coordinates of polygons where

A=[ 1 1;
    2 0;
    4 0;
    10 1;
    0 0;
    1 5;
    11 2;
    0 2;
    2 2;
     .
     .
     .
    x y ]

and C such that it contains the collection of vertex locations in A of a polygon where C is something like:

C = {[ 2, 5, 8, 9]
           .
           .
           .
     [x,y locations in A]}

C{1} contains the coordinates (2,0), (0,0), (0,2), and (2,2) from A. I want to take say, the first elements of C{1}, and sort C such that the remaining element order in C{1} moves clockwise (or counter-clockwise) in terms of element location with respect to polygon generation. So C{1}(1)=2 (2,0), and the remaining elements would follow as such:

C{1}(2)=9 (2,2)
C{1}(3)=8 (0,2)
C{1}(4)=5 (0,0)

[Sara]

Do you have the mapping toolbox?

[Sean]

Yes.

[Sean]

Is is possible to use the convexHull function with vertices of your choosing?

[Sara]

I was thinking at poly2cw actually. it will order the vertexes in the clock wise order, then you can reorganize it so you have first the vertex of your choice

[Sean]

That is clever, cheers.

[Sean]

For future reference, something like this

v = cell(size(C)); 
for j=1:length(C)
frodo = C{j};
aragorn_x = new_pts(frodo,1);
aragorn_y = new_pts(frodo,2);

DT = delaunayTriangulation(aragorn_x,aragorn_y);
[K,v{j}] = convexHull(DT);
end

turned out to be valuable (with the help of Jos (10584)).