Workspace and variable management in MATLAB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the MATLAB workspace?

The MATLAB workspace is the area where all variables created during a session are stored and can be accessed or modified.

beginner

How do you list all variables currently in the MATLAB workspace?

Use the command whos to list all variables with details like size and type.

beginner

How can you clear a specific variable from the workspace?

Use the command clear variableName to remove a specific variable from the workspace.

beginner

What command clears all variables from the workspace?

The command clear without arguments removes all variables from the workspace.

beginner

How do you save workspace variables to a file?

Use save filename to save all workspace variables to a file named filename.mat.

Which command shows detailed information about variables in the MATLAB workspace?

A whos

B clear

C load

D save

The whos command lists all variables with details like size and type.

What happens when you run clear with no arguments?

A Lists all variables

B Clears only the command window

C Saves all variables to a file

D Clears all variables from the workspace

Running clear without arguments removes all variables from the workspace.

How do you remove only the variable named 'data' from the workspace?

A clear data

B clear all

C delete data

D remove data

Use clear data to remove the variable named 'data' only.

Which command saves workspace variables to a file?

A clear filename

B save filename

C load filename

D export filename

The save filename command saves all workspace variables to a file.

What is the purpose of the MATLAB workspace?

A To write scripts

B To display graphics

C To store variables during a session

D To compile code

The workspace stores all variables created during a MATLAB session.

Explain how to manage variables in the MATLAB workspace, including listing, clearing, and saving variables.

Think about commands that help you see, remove, and save variables.

Describe what the MATLAB workspace is and why it is important for variable management.

Imagine the workspace as your working desk where you keep all your notes (variables).

Practice

1. What does the clear command do in MATLAB workspace?

easy

A. Removes variables from the workspace

B. Displays all variables in the workspace

C. Saves variables to a file

D. Loads variables from a file

Solution

1. Step 1: Understand the purpose of clear

   The clear command is used to remove variables from the workspace, freeing memory.

2. Step 2: Differentiate from other commands

   who and whos display variables, save saves variables, and load loads variables.

3. Final Answer:

   Removes variables from the workspace -> Option A

4. Quick Check:

   clear removes variables [OK]

Hint: Clear removes variables, not shows or saves [OK]

Common Mistakes:

• Confusing clear with who or whos
• Thinking clear saves variables
• Assuming clear loads variables

2. Which of the following is the correct syntax to list all variables in the workspace with details?

easy

A. listvars

B. whos

C. showvars()

D. vars()

Solution

1. Step 1: Recall commands to list variables

   who lists variable names; whos lists variables with details like size and type.

2. Step 2: Identify correct syntax

   whos is the correct command; others are invalid or do not exist in MATLAB.

3. Final Answer:

   whos -> Option B

4. Quick Check:

   whos lists variables with details [OK]

Hint: Use whos to see detailed variable info [OK]

Common Mistakes:

• Using non-existent commands like listvars
• Confusing who with whos for details
• Adding parentheses to whos (it's not a function)

3. Consider the following MATLAB commands:

a = 5;
b = 10;
clear a;
whos

What variables will whos display?

medium

A. No variables

B. Only a

C. a and b

D. Only b

Solution

1. Step 1: Analyze the commands

   Variables a and b are created. Then clear a removes a from workspace.

2. Step 2: Determine remaining variables

   After clearing a, only b remains. whos will show b only.

3. Final Answer:

   Only b -> Option D

4. Quick Check:

   clear a removes a, so only b remains [OK]

Hint: Clear specific variable removes only that variable [OK]

Common Mistakes:

• Assuming clear removes all variables
• Thinking clear a clears variable b too
• Expecting whos to show cleared variables

4. What is wrong with this MATLAB code snippet?

clear x y
x = 10;
load('data.mat')

Assuming data.mat contains variable y with value 5.

medium

A. clear cannot take multiple variables

B. No error, code works as expected

C. load overwrites variable y after clear

D. Variable x is cleared after load

Solution

1. Step 1: Understand clear and load behavior

   clear x y removes variables x and y. Then x is assigned 10.

2. Step 2: Effect of load on variables

   load('data.mat') loads variable y from file, overwriting any existing y. Since y was cleared, it is now restored from file.

3. Step 3: Identify the issue

   The variable y is overwritten by load, which may be unexpected if user thought clear removed it permanently.

4. Final Answer:

   load overwrites variable y after clear -> Option C

5. Quick Check:

   load restores variables from file, overwriting workspace [OK]

Hint: Load restores variables, overwriting existing ones [OK]

Common Mistakes:

• Thinking clear cannot clear multiple variables
• Assuming load does not overwrite variables
• Believing x is cleared after load

5. You want to save only variables a and b from your workspace to a file named myvars.mat. Which command should you use?

hard

A. save myvars.mat a b

B. save('myvars.mat', 'a', b)

C. save('myvars.mat')

D. save('myvars.mat', a, b)

Solution

1. Step 1: Recall save syntax for specific variables

   To save specific variables, list their names without quotes after the filename without parentheses.

2. Step 2: Analyze options

   save myvars.mat a b uses correct syntax: save myvars.mat a b. save('myvars.mat', 'a', b) uses quotes but parentheses, which is invalid syntax in MATLAB. save('myvars.mat') saves all variables. save('myvars.mat', a, b) passes variables as values, which is incorrect.

3. Final Answer:

   save myvars.mat a b -> Option A

4. Quick Check:

   Use save filename var1 var2 to save specific variables [OK]

Hint: Use save filename var1 var2 without parentheses [OK]

Common Mistakes:

• Using parentheses with save command
• Putting variable names in quotes inside parentheses
• Saving all variables unintentionally