function S=sier(A)
%Sierpinski triangle.  -JJL
[M,N]=size(A);
if M~=2,error('Incorrect data format'),end;
b1=repmat([.5,0]',1,N);
b2=repmat([0,.5]',1,N);
y1=.5*A;
y2=y1+b1;
y3=y1+b2;
x=[y1(1,:),y2(1,:),y3(1,:)];y=[y1(2,:),y2(2,:),y3(2,:)];
plot(x,y,'.')
if nargout>0,S=[x;y];end