function [x] = L1_ball(rho)

t = 0:.01:4;
[m,n] = size(t);

for i=1:n
  if t(i) <= 1 
    x(1,i) = rho*(1-t(i));
    x(2,i) = -rho*(1-t(i)) + rho;
  elseif t(i) <= 2  
    x(1,i) = (1-t(i))*rho;
    x(2,i) = rho*(1-t(i)) + rho;
  elseif t(i) <= 3
    x(1,i) = - rho + (t(i)-2)*rho;
    x(2,i) = (2-t(i))*rho;
  else
    x(1,i) = (t(i)-3)*rho;
    x(2,i) = -rho + (t(i)-3)*rho;
  end
end