Tutorial · Intermediate · 10 min

Bring it to life: animations

Call animate(seconds) and your whole script re-runs every frame with t set to the time. Anything that depends on t moves.

1. The time variable t

   animate(4) makes a 4-second loop. Use t anywhere — here it shifts a sine wave. The bar under the figure lets you pause, scrub and change the speed.

   animate(4)
   x = linspace(0, 4*pi, 300);
   plot(x, sin(x - 2*pi*t/4), 'LineWidth', 2)
   ylim([-1.2 1.2])
   title(sprintf('t = %.2f s', t))

   Try it ↗

2. A point moving along a curve

   Draw the path once, then a marker at the position for the current time.

   animate(6)
   s = linspace(0, 2*pi, 400);
   plot(cos(s), sin(2*s), 'LineWidth', 1.5)
   hold on
   p = 2*pi*t/6;
   scatter(cos(p), sin(2*p), 120, 'r', 'filled')
   hold off
   axis equal
   title('A figure-eight path')

   Try it ↗

3. Changing a parameter

   Time can drive any parameter. Here the damping of an oscillation slowly increases.

   animate(8)
   x = linspace(0, 10, 400);
   gamma = 0.05 + 0.4 * t / 8;
   plot(x, exp(-gamma*x) .* cos(3*x), 'LineWidth', 2)
   ylim([-1 1])
   title(sprintf('damping γ = %.2f', gamma))

   Try it ↗

4. Spinning a 3D view

   Make the camera angle depend on t for a turntable effect. Use Export → Record animation to save it as a video.

   animate(10)
   [X, Y] = meshgrid(linspace(-3, 3, 45));
   surf(X, Y, peaks(X, Y))
   shading flat
   colormap viridis
   view(36*t, 30)
   title('A turntable view')

   Try it ↗