为什么出不来图形，

clear all;
x(1)=0.3342;
y(1)=0.4525;
z(1)=0.3652;
for n=1:100
    if 0<=x(n)<0.5&0<=y(n)<0.5
        x(n+1)=2*x(n);
        y(n+1)=2*y(n);
        z(n+1)=0.25*z(n);
    elseif 0<=x(n)<0.5&0.5<=y(n)<=1
        x(n+1)=2*x(n);
        y(n+1)=2*y(n)-1;
        z(n+1)=0.25*z(n)+0.5;
    elseif 0.5<=x(n)<=1&0<=y(n)<0.5
        x(n+1)=2*x(n)-1;
        y(n+1)=2*y(n);
        z(n+1)=0.25*z(n)+0.25;
    else 0.5<=x(n)<=1&0.<=y(n)<=1
         x(n+1)=2*x(n)-1;
         y(n+1)=2*y(n)-1;
         z(n+1)=0.25*z(n)+0.75;
  end
plot3(x,y,z);