function ifs4(M,iters,xmin,xmax,ymin,ymax);
%For a fern enter
%M=[0 0 0 .16 0 0 .01;
%.85 .04 -.04 .85 0 .4 .85;
%.2 -.26 .23 .22 0 .4 .07;
%-.15 .28 .26 .24 0 .11 .07];
%and call ifs4(M,10^6,-1,1,0,2.6);
viewsize=700;
IFSimage = ones(viewsize,viewsize,3);
thresh=100;
[X Y]=size(M);
x = rand(1);
y = rand(1);
for n=1:iters
    r = rand(1);
    p=0;
    k=0;
    while (p<=r)&(k<X) %use the random number to work down 
        k=k+1; %the cumulative probabilites to choose a row
        p=p+M(k,7);
    end
    newx=M(k,1)*x+M(k,2)*y+M(k,5); %now iterate once
    newy=M(k,3)*x+M(k,4)*y+M(k,6);
    x = newx;
    y = newy;
    if n > (thresh)&(x>=xmin)&(x<=xmax)&(y>=ymin)&(y<=ymax)
        IFSimage(int16(viewsize*(1-(y-ymin)/(ymax-ymin))+1),int16(viewsize*(x-xmin)/(xmax-xmin)+1),:) = 0;
    end
end
image(IFSimage);