function trainwaves
X=0:0.01:20;
f = 5.25;
P = 1/f;
w = 2*pi*f;
v = 10;
k = w/v;
A = 1;
Rd = A*exp((1i*k)*(X-20));
zeta1d = k*(X-20)+pi/2;
zeta2d = k*(X-20)-24.5*pi;
Re = A*exp((1i*k)*X);
zeta1e = k*X-pi/2;
zeta2e = k*X+24.5*pi;
dt = P/8;
iwd = 1i*w;
iwe = -1i*w;
t = 0;
pause on
for n=1:200
    t = t + dt;
    Z = 1./(1+exp(-20*(zeta1d+w*t)));
    Z = Z./(1+exp(20*(zeta2d+w*t)));   % descomente para opção 1
    T = exp(iwd*t);
    Yd = real(Rd.*T).*Z;
    
    Z = 1./(1+exp(20*(zeta1e-w*t)));
    Z = Z./(1+exp(-20*(zeta2e-w*t)));  % descomente para opção 1
    T = exp(iwe*t);
    Ye = real(Re.*T).*Z;

    plot(X,Yd+Ye)
    axis image
    axis([0 20 -2 2])
    axis off
    pause(0.1)
%    if (n==170), hold on; dt = dt/4; end;  % comente para opção 1
end;
pause off
hold off