function ccollatz(xmin,xmax,ymin,ymax, maxiter);
%Example ccollatz(-2,2,-2,2,300)
nx = 400;
ny = 400;
ColorMset = zeros(ny,nx,3);
wb = waitbar(0,'Please wait...');
for iy = 1:ny
  cy = ymin + iy*(ymax - ymin)/(ny - 1);
  for ix= 1:nx
    cx = xmin + ix*(xmax - xmin)/(nx - 1);
    k = Mlevel(cx,cy,maxiter);
    if k == 0 
        ColorMset(iy,ix,:) = 0;
    else    
        ColorMset(iy,ix,1) = abs(sin(2*k/10));
        ColorMset(iy,ix,2) = abs(sin(2*k/10+pi/4));
        ColorMset(iy,ix,3) = abs(cos(2*k/10));
    end
  end
  waitbar(iy/ny,wb)
end
close(wb);
image(ColorMset);
function [potential] = Mlevel(cx,cy,maxiter)
z = complex(cx,cy);
iter = 0;
while (iter < maxiter)&(abs(z) < 100)
   z = (2+7*z-(2+5*z)*cos(pi*z))/4;
   iter = iter+1;
end
if iter < maxiter
    potential = iter;
else
    potential = 0;
end