Animation basics in MATLAB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this MATLAB animation code?

Consider the following MATLAB code snippet that animates a moving point on a plot. What will be the final position of the point after the loop finishes?

MATLAB

figure;
h = plot(0,0,'ro','MarkerSize',10,'MarkerFaceColor','r');
xlim([0 10]); ylim([0 10]);
for k = 1:5
    set(h, 'XData', k, 'YData', k);
    pause(0.1);
end
finalX = get(h, 'XData');
finalY = get(h, 'YData');

A [5, 5]

B [1, 1]

C [10, 10]

D [0, 0]

💡 Hint

The loop moves the point from (1,1) to (5,5) step by step.

The loop updates the point's X and Y coordinates from 1 to 5. After the loop ends, the point is at (5,5).

🧠 Conceptual

intermediate

Which MATLAB function is essential to update graphics in an animation loop?

In MATLAB animations, which function forces the figure window to refresh and show updated graphics immediately inside a loop?

A clf

B pause

C refreshdata

D drawnow

💡 Hint

This function processes any pending callbacks and updates the figure window.

The drawnow function forces MATLAB to update the figure window immediately, which is essential for smooth animations.

🔧 Debug

advanced

Why does this MATLAB animation code freeze and not update the plot?

Examine the code below. It is supposed to animate a point moving along the x-axis, but the plot does not update during the loop. What is the cause?

MATLAB

figure;
h = plot(0,0,'bo','MarkerSize',8);
xlim([0 10]); ylim([0 1]);
for x = 1:10
    set(h, 'XData', x);
end

A The pause duration is too short to see updates

B The plot handle h is not valid

C Missing drawnow command inside the loop

D xlim and ylim are set incorrectly

💡 Hint

MATLAB needs a command to refresh the figure window during loops.

Without drawnow, MATLAB delays updating the figure until the loop ends, causing the animation to freeze.

📝 Syntax

advanced

Which option correctly creates a MATLAB animated line and adds points in a loop?

Select the code snippet that correctly creates an animated line and adds points to it inside a loop.

A

h = animatedline;
for k = 1:5
    addpoints(h, k, sin(k));
    pause(0.1);
end

B

h = animatedline();
for k = 1:5
    addpoints(h, k, sin(k));
    drawnow;
end

C

h = animatedline();
for k = 1:5
    addpoints(h, k, sin(k));
end
drawnow;

D

h = animatedline();
for k = 1:5
    addpoints(h, k, sin(k));
    refreshdata;
end

💡 Hint

The animated line needs drawnow inside the loop to update the plot.

Option B correctly creates the animated line, adds points, and calls drawnow inside the loop for smooth animation.

🚀 Application

expert

How many frames will this MATLAB animation produce?

Given the code below, how many frames will be displayed in the animation?

MATLAB

figure;
h = plot(0,0,'ko','MarkerSize',12);
xlim([0 20]); ylim([0 20]);
for i = 1:10
    for j = 1:5
        set(h, 'XData', i*j, 'YData', i+j);
        drawnow;
        pause(0.05);
    end
end

A 50

B 15

C 10

D 5

💡 Hint

Count how many times the inner loop runs and how many times the outer loop runs.

The outer loop runs 10 times and the inner loop runs 5 times each, so total frames = 10 * 5 = 50.