%% Folding animation
a = 0.1;
b = 0.1;
c = 18;
f = @(t,y) rossler(t,y,a,b,c);

% Initial line
M = 1000; % Number of points in line
x0 = [zeros(M,1), linspace(-26, -12, M)', zeros(M,1)];

dt = 0.05;
N = 600;

X = x0;

% Create figure
figure;
hold on;
grid on;
xlabel('r = sqrt(x^2 + y^2)');
ylabel('log(z)');
axis([0,30,-10,5]);

% GIF settings
filename = 'rossler_folding_wiki.gif';
delay = 0.05;

for i = 1:N
    Xnew = zeros(size(X));
    for j = 1:M
        [~, y] = ode45(f, [0, dt], X(j,:));
        Xnew(j,:) = y(end,:);
    end
    X = Xnew;

    r = sqrt(X(:,1).^2 + X(:,2).^2);
    z = log(X(:,3));
    cla;
    plot(r, z, '.-');
    title(sprintf("Folding in Rossler attractor: t = %.2f", dt * i));
    drawnow;

    % Capture frame
    frame = getframe(gcf);
    im = frame2im(frame);
    [A,map] = rgb2ind(im,256);

    % Write to GIF
    if i == 1
        imwrite(A, map, filename, 'gif', 'LoopCount', Inf, 'DelayTime', delay);
    else
        imwrite(A, map, filename, 'gif', 'WriteMode', 'append', 'DelayTime', delay);
    end
end

function dydx=rossler(t,y,a,b,c)
%   Integrate phase point (y(1)=x, y(2)=y, y(3)=z)
dydx(1,1)=-y(2)-y(3);
dydx(2,1)=y(1)+a*y(2);
dydx(3,1)=b+y(3)*(y(1)-c);

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