function []=conchoid;
% Draw a surface in 2 parameter uv space

[u,v]=meshgrid(0:0.1:6*pi,0:0.1:2.01*pi);
k=1.2; k2=1.2; a=1.5;  % a=0.5
x=k.^u.*(1+cos(v)).*cos(u);
y=k.^u.*(1+cos(v)).*sin(u);
z=k.^u.*sin(v)-a*k2.^u;

surf(x,y,z)
 colorbar 'v';
 set(gcf,'color','blue');
 %shading interp;
 hold on;
 %colorbar v:
view(120,20);
camlight left;
axis off;
grid off;

% Draw a set of axes
%xmax=max(max(x)); ymax=max(max(y)); zmax=max(max(z));  
%line([0,xmax],[0,0],[0,0],'LineWidth',2,'Color','r');
%line([0,0],[0,ymax],[0,0],'LineWidth',2,'Color','r');
%line([0,0],[0,0],[0,zmax],'LineWidth',2,'Color','r');
%text(xmax+0.1,0,0,'X','Color','r','FontSize',15);
%text(0,ymax+0.1,0,'Y','Color','r','FontSize',15);
%text(0,0,zmax+0.01,'Z','Color','r','FontSize',15);
%xlabel('x'); ylabel('y'); zlabel('z');
title('Conchoid');
% --------------------------------------------------------