Cantor set

Based on the recursion technique, compute the cantor set.The Cantor set is obtained by
removing from the segment [0,1] the middle thirds.For the given N (the number of steps), your code
should display a narrow black rectangle with removed pieces (in
white). As the final outcome, plot 6 first steps (in the same figure) of construction
of the Cantor set. Your graph should be a column consisting of 6 stripes.

I don't know how to keep doing this question..can anyone help me please?

function Z=cantor_set(n)
x1=0; y1=0;
x2=1; y2=0;
x3=1; y3=1;
x4=0; y4=1;
figure(1)
hold on
set(gca,'xtick',[],'ytick',[]);
set(gca,'XColor','w','YColor','w');
fill([x1 x2 x3 x4], [y1 y2 y3 y4],'k');
rectangle1(x1,y1,x2,y2,x3,y3,x4,y4,0,Lmax);
hold off
    function Z=rectangle1(x1,y1,x2,y2,x3,y3,x4,y4,n,Lmax)

[Walter Roberson]

Lam is working on the same question. http://www.mathworks.com/matlabcentral/answers/38780-cantor-set-problem