From your query, it looks like the set of points S(0) is defined by the (x,y) coordinates that are randomly generated in your code.
But, does it look similar to a circle? No is my hunch. If you wanted to generate a set of points that look similar to a circle , you could use something similar to the below:
t = 2*pi*rand(n,1);
r = R*sqrt(rand(n,1));
x = x0 + r.*cos(t);
y = y0 + r.*sin(t);
[k,v] = boundary(_) returns a scalar v, which is the area which boundary k encloses.
[k, v] = boundary(x,y);
Based on your existing code's structure, it seems that you are trying to estimate pi from this area calculation.
Here, the returned 'v' will be an estimate of pi/4. (If R=0.5)
Hence 4 times 'v' will be an estimate of pi.
Hope it helps!