den=[conv([1,5],conv([1,20],[1,50])),0,0];
num=[1,0.125]; G=tf(num,den);
hold off; rlocus(G);  axis('square')
[K,P]=rlocfind(G) % Selecting point 1

[xx,yy]=rlasymp(G); hold on; plot(xx,yy,':')