Multiple plots (hold on) in MATLAB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to plot two lines on the same figure.

MATLAB

x = 1:5;
y = x.^2;
plot(x, y);
hold [1];
y2 = x.^3;
plot(x, y2);

Drag options to blanks, or click blank then click option'

Aclear

Bon

Coff

Dall

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'hold off' erases the previous plot before drawing the new one.

Using hold on allows multiple plots on the same figure without erasing the previous plot.

2fill in blank

medium

Complete the code to plot a sine and cosine on the same graph.

MATLAB

x = linspace(0, 2*pi, 100);
plot(x, sin(x));
hold [1];
plot(x, cos(x));

Drag options to blanks, or click blank then click option'

Aoff

Bclear

Con

Dreset

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'hold off' causes the first plot to disappear.

hold on keeps the first plot so the second plot appears on the same axes.

3fill in blank

hard

Fix the error in the code to plot two lines without erasing the first.

MATLAB

x = 0:0.1:1;
plot(x, x);
hold [1];
plot(x, x.^2);

Drag options to blanks, or click blank then click option'

Aon

Boff

Cclear

Dhold

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'hold off' erases the first plot.

The correct command is hold on to keep the first plot visible.

4fill in blank

hard

Fill both blanks to plot three lines on the same figure.

MATLAB

x = 1:4;
plot(x, x);
hold [1];
plot(x, x.^2);
hold [2];
plot(x, x.^3);

Drag options to blanks, or click blank then click option'

Aon

Boff

Chold

Dclear

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'hold off' before the second plot clears previous plots.

Using hold on before the second plot keeps the first plot visible, and hold off before the third plot releases the hold so the third plot replaces the previous plots.

5fill in blank

hard

Fill all three blanks to create a figure with multiple plots and then release hold.

MATLAB

x = 0:pi/4:2*pi;
plot(x, sin(x));
hold [1];
plot(x, cos(x));
hold [2];
plot(x, tan(x));
hold [3];

Drag options to blanks, or click blank then click option'

Aon

Boff

Chold

Dclear

Attempts:

3 left

💡 Hint

Common Mistakes

Not turning hold off at the end causes all future plots to overlay.

Use hold on to add plots without erasing, then hold off to release hold.

Practice

1. What does the hold on command do in MATLAB plotting?

easy

A. Clears the current figure before plotting new data.

B. Allows multiple plots to be drawn on the same figure without erasing previous plots.

C. Saves the current plot to a file.

D. Changes the color of the plot lines automatically.

Solution

1. Step 1: Understand the purpose of hold on

   The hold on command tells MATLAB to keep the current plot and add new plots on top of it.

2. Step 2: Compare with other options

   Other commands like hold off or default plotting clear the figure before new plots, so they do not allow multiple plots together.

3. Final Answer:

   Allows multiple plots to be drawn on the same figure without erasing previous plots. -> Option B

4. Quick Check:

   hold on = multiple plots on one figure [OK]

Hint: Remember: hold on means keep adding plots [OK]

Common Mistakes:

• Thinking hold on clears the figure
• Confusing hold on with saving plots
• Assuming hold on changes plot colors

2. Which of the following is the correct way to plot two lines on the same figure in MATLAB?

easy

A. plot(x1, y1); hold on; plot(x2, y2); hold off;

B. hold on; plot(x1, y1); hold off; plot(x2, y2);

C. plot(x1, y1); plot(x2, y2);

D. plot(x1, y1); hold off; plot(x2, y2);

Solution

1. Step 1: Identify the correct sequence to keep multiple plots

   Using hold on after the first plot keeps it visible for the second plot.

2. Step 2: Confirm proper use of hold off

   Calling hold off after plotting both lines resets plotting behavior for future plots.

3. Final Answer:

   plot(x1, y1); hold on; plot(x2, y2); hold off; -> Option A

4. Quick Check:

   Use hold on between plots to combine them [OK]

Hint: Use hold on right after first plot to add more [OK]

Common Mistakes:

• Not using hold on before second plot
• Using hold off too early
• Plotting without hold on clears previous plot

3. What will be the output of the following MATLAB code?

t = 0:0.1:1;
plot(t, t);
hold on;
plot(t, t.^2);

medium

A. Two plots will appear: a straight line and a curve on the same figure.

B. Only the plot of t vs t^2 will be shown.

C. An error will occur because hold on is used incorrectly.

D. Only the plot of t vs t will be shown.

Solution

1. Step 1: Analyze the first plot command

   The first plot draws a straight line y = t on the figure.

2. Step 2: Understand the effect of hold on and second plot

   Using hold on keeps the first plot visible, so the second plot y = t^2 is drawn on the same figure as a curve.

3. Final Answer:

   Two plots will appear: a straight line and a curve on the same figure. -> Option A

4. Quick Check:

   hold on keeps previous plot, so both appear [OK]

Hint: hold on keeps old plots visible for new ones [OK]

Common Mistakes:

• Thinking only last plot shows
• Assuming hold on causes error
• Confusing plot commands order

4. Identify the error in this MATLAB code that tries to plot two lines on the same figure:

plot(x, y1)
hold off
plot(x, y2)

medium

A. There is no error; the code works correctly.

B. The variable x is not defined.

C. hold off should be called before the first plot.

D. hold off should be replaced with hold on to keep both plots visible.

Solution

1. Step 1: Understand the effect of hold off

   Calling hold off resets plotting to clear the figure before the next plot.

2. Step 2: Identify correct command to keep plots

   To keep both plots visible, hold on should be used instead of hold off.

3. Final Answer:

   hold off should be replaced with hold on to keep both plots visible. -> Option D

4. Quick Check:

   Use hold on to combine plots, not hold off [OK]

Hint: hold off clears plots; use hold on to keep them [OK]

Common Mistakes:

• Using hold off instead of hold on
• Thinking hold off adds plots
• Ignoring hold commands altogether

5. You want to plot three different data sets on the same figure with different colors and then reset plotting to default for future plots. Which sequence of commands is correct?

hard

A. plot(x1, y1, 'r'); plot(x2, y2, 'g'); plot(x3, y3, 'b'); hold on; hold off;

B. hold on; plot(x1, y1, 'r'); plot(x2, y2, 'g'); plot(x3, y3, 'b');

C. plot(x1, y1, 'r'); hold on; plot(x2, y2, 'g'); plot(x3, y3, 'b'); hold off;

D. plot(x1, y1, 'r'); hold off; plot(x2, y2, 'g'); hold on; plot(x3, y3, 'b');

Solution

1. Step 1: Use hold on after first plot to combine multiple plots

   After plotting the first data set, hold on keeps the figure active for additional plots.

2. Step 2: Plot all data sets with specified colors and then reset with hold off

   Plotting the second and third data sets adds them to the same figure. Calling hold off resets plotting behavior for future plots.

3. Final Answer:

   plot(x1, y1, 'r'); hold on; plot(x2, y2, 'g'); plot(x3, y3, 'b'); hold off; -> Option C

4. Quick Check:

   hold on after first plot, hold off after last plot [OK]

Hint: hold on after first plot, hold off after last [OK]

Common Mistakes:

• Not calling hold off after multiple plots
• Calling hold on before first plot
• Mixing hold on and hold off incorrectly