Workspace and variable management in MATLAB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a variable named x with the value 10.

MATLAB

x = [1];

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

Ax

B'x'

C10

D10;

Attempts:

3 left

💡 Hint

Common Mistakes

Putting the number in quotes, which creates a string instead of a number.

Using the variable name on the right side instead of a value.

The variable x is assigned the numeric value 10 using x = 10;.

2fill in blank

medium

Complete the code to clear the variable y from the workspace.

MATLAB

clear [1];

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

Ay

Bx

Cclear

Dworkspace

Attempts:

3 left

💡 Hint

Common Mistakes

Using clear without specifying the variable name clears all variables.

Typing the command incorrectly, like clear workspace.

The command clear y; removes the variable y from the workspace.

3fill in blank

hard

Fix the error in the code to list all variables currently in the workspace.

MATLAB

vars = [1];

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

Awhos

Bwho()

Clistvars

Dvariables

Attempts:

3 left

💡 Hint

Common Mistakes

Using who() with parentheses, which is incorrect syntax in MATLAB.

Using non-existent commands like listvars or variables.

The whos command lists detailed information about variables in the workspace.

4fill in blank

hard

Fill both blanks to save variables a and b to a file named data.mat.

MATLAB

save('[1]', [2]);

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

Adata.mat

B'a', 'b'

Da b

Attempts:

3 left

💡 Hint

Common Mistakes

Putting variable names in quotes as a single string.

Not quoting the filename.

Separating variable names with commas.

The save command saves variables a and b to the file data.mat. Variable names are listed without quotes separated by spaces.

5fill in blank

hard

Fill all three blanks to load variables m and n from the file mydata.mat into the workspace.

MATLAB

load('[1]', '[2]', '[3]');

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

Amydata.mat

Bm

Cn

Ddata.mat

Attempts:

3 left

💡 Hint

Common Mistakes

Not quoting the filename or variable names.

Using the wrong filename.

Listing variables without quotes.

The load command loads variables m and n from the file mydata.mat. The filename and variable names are all strings in quotes.

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