Only one plot when expecting multiple

Why do I get only plot if I use this script? I try to get one plot for the value of a at the beginning

while a>0 
  while z > 0
     plot(x{1,z}(:,1),y{a,z}(:,1))
     hold on
     z = z-1;
  end 
  hold off
  z = B;
  a = a-1;
end

Answer 1

[KSSV]

Remove hold off from the loop.

[Brecht Leenmans]

I like to obtain one plot for every start value of a and on each plot iI like to have an amount of z 2D lines.