Labels, title, and legend in MATLAB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What function in MATLAB is used to add a title to a plot?

The title() function adds a title to the current plot in MATLAB.

beginner

How do you label the x-axis and y-axis in a MATLAB plot?

Use xlabel('text') to label the x-axis and ylabel('text') to label the y-axis.

beginner

What is the purpose of the legend() function in MATLAB?

The legend() function adds a legend to the plot, which explains the meaning of different plot lines or markers.

intermediate

How can you customize the font size of the title in MATLAB?

You can customize the font size by using title('text', 'FontSize', size), where size is a number representing the font size.

intermediate

What happens if you call legend() without any arguments?

MATLAB automatically creates a legend using the labels from the plotted data series if available.

Which MATLAB function adds a label to the y-axis of a plot?

A legend()

B xlabel()

C ylabel()

D title()

ylabel() adds a label to the y-axis.

How do you add a legend to a MATLAB plot?

A xlabel()

B legend()

C title()

D ylabel()

legend() adds a legend explaining plot lines or markers.

What does the title() function do in MATLAB?

A Adds a title to the plot

B Labels the x-axis

C Creates a legend

D Labels the y-axis

title() adds a title to the current plot.

Which property can you set to change the font size of a plot title?

A 'FontSize'

B 'Color'

C 'LineWidth'

D 'MarkerSize'

Use 'FontSize' to change the font size of the title.

If you plot multiple lines and call legend() without arguments, what happens?

A The plot is cleared

B No legend is created

C An error occurs

D MATLAB creates a legend using the plot labels

MATLAB automatically generates a legend from the plotted data labels.

Explain how to add and customize labels, title, and legend in a MATLAB plot.

Think about the functions for labeling and how to change their appearance.

Describe what happens when you call legend() without any arguments after plotting multiple lines.

Consider how MATLAB helps you identify plot lines easily.

Practice

1. Which MATLAB function is used to add a label to the x-axis of a plot?

easy

A. xlabel

B. ylabel

C. title

D. legend

Solution

1. Step 1: Understand axis labeling functions

   In MATLAB, xlabel labels the x-axis, ylabel labels the y-axis, title adds a main heading, and legend explains plot lines.

2. Step 2: Identify the function for x-axis label

   The function xlabel is specifically designed to add a label to the x-axis.

3. Final Answer:

   xlabel -> Option A

4. Quick Check:

   Label x-axis = xlabel [OK]

Hint: Use xlabel for x-axis label, ylabel for y-axis [OK]

Common Mistakes:

• Confusing xlabel with ylabel
• Using title instead of axis labels
• Using legend for axis labels

2. Which of the following is the correct syntax to add a legend to a plot with two lines labeled 'Data1' and 'Data2'?

easy

A. legend{'Data1', 'Data2'}

B. legend = ('Data1', 'Data2')

C. legend['Data1', 'Data2']

D. legend('Data1', 'Data2')

Solution

1. Step 1: Recall correct legend syntax

   In MATLAB, the function legend is called with parentheses and string arguments to label plot lines.

2. Step 2: Identify correct syntax

   The correct syntax uses parentheses and comma-separated strings: legend('Data1', 'Data2'). Other options use invalid assignment or brackets.

3. Final Answer:

   legend('Data1', 'Data2') -> Option D

4. Quick Check:

   legend('labels') uses parentheses [OK]

Hint: Use legend('label1', 'label2') with parentheses [OK]

Common Mistakes:

• Using assignment '=' instead of function call
• Using square or curly brackets
• Missing quotes around labels

3. What will be the title of the plot after running this MATLAB code?

plot(1:5, [2 4 6 8 10]);
title('Sales Over Time');

medium

A. plot(1:5, [2 4 6 8 10])

B. Sales Over Time

C. 1:5

D. No title

Solution

1. Step 1: Understand the title function

   The title function sets the main heading of the plot to the given string.

2. Step 2: Check the given code

   The code calls title('Sales Over Time'), so the plot's title will be exactly 'Sales Over Time'.

3. Final Answer:

   Sales Over Time -> Option B

4. Quick Check:

   title('text') sets plot title [OK]

Hint: title('text') sets the plot's main heading [OK]

Common Mistakes:

• Confusing title with axis labels
• Expecting variable values as title
• No title if title function missing

4. Identify the error in this MATLAB code snippet:

plot(x, y);
xlabel = 'Time';
ylabel('Value');
legend('Line1');

medium

A. Using assignment '=' with xlabel instead of function call

B. Missing ylabel function call

C. legend syntax is incorrect

D. plot function is missing arguments

Solution

1. Step 1: Check xlabel usage

   The code uses xlabel = 'Time'; which assigns a string to variable xlabel instead of calling the function xlabel('Time').

2. Step 2: Verify other lines

   ylabel('Value') and legend('Line1') are correctly called as functions. The plot function has arguments x, y assumed defined.

3. Final Answer:

   Using assignment '=' with xlabel instead of function call -> Option A

4. Quick Check:

   Use xlabel('text'), not xlabel = 'text' [OK]

Hint: Call xlabel as function: xlabel('text'), not assignment [OK]

Common Mistakes:

• Assigning xlabel instead of calling function
• Confusing ylabel syntax
• Incorrect legend usage

5. You have plotted two data sets on the same graph using:

plot(x, y1, '-r', x, y2, '-b');

How do you add a title 'Comparison', label the x-axis as 'Time', the y-axis as 'Value', and add a legend with labels 'Data1' and 'Data2'?

hard

A. title = 'Comparison'; xlabel = 'Time'; ylabel = 'Value'; legend = ('Data1', 'Data2');

B. title('Comparison'); xlabel('Time'); ylabel('Value'); legend(['Data1', 'Data2']);

C. title('Comparison'); xlabel('Time'); ylabel('Value'); legend('Data1', 'Data2');

D. title('Comparison'); xlabel('Time'); ylabel('Value'); legend{'Data1', 'Data2'};

Solution

1. Step 1: Use correct function calls for labels and title

   Functions title, xlabel, and ylabel require parentheses with string arguments.

2. Step 2: Use correct legend syntax

   The legend function takes comma-separated strings inside parentheses, not assignment or brackets.

3. Final Answer:

   title('Comparison'); xlabel('Time'); ylabel('Value'); legend('Data1', 'Data2'); -> Option C

4. Quick Check:

   Use function calls with parentheses for labels and legend [OK]

Hint: Use function calls with parentheses for all labels and legend [OK]

Common Mistakes:

• Assigning strings instead of calling functions
• Using brackets or braces for legend
• Missing quotes around labels