Variable creation and assignment in MATLAB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a variable in MATLAB?

A variable in MATLAB is a name that stores data or values which can be used and changed during the program.

beginner

How do you create and assign a value to a variable in MATLAB?

You create a variable by writing its name, then an equal sign (=), and then the value you want to store. For example: x = 5;

beginner

What happens if you assign a new value to an existing variable in MATLAB?

The old value is replaced by the new value. MATLAB updates the variable to hold the new data.

beginner

Can variable names in MATLAB contain spaces or start with a number?

No, variable names cannot contain spaces and cannot start with a number. They must start with a letter and can include letters, numbers, and underscores.

beginner

What is the difference between x = 5 and x = '5' in MATLAB?

x = 5 assigns the number 5 to x, while x = '5' assigns the character '5' (a text) to x.

Which of the following is a valid variable name in MATLAB?

A var-1

B 1stVar

C my var

D my_var1

Variable names must start with a letter and cannot contain spaces or special characters like '-'.

What does the statement a = 10; do in MATLAB?

A Creates a variable 'a' and assigns it the value 10

B Deletes the variable 'a'

C Prints the value 10

D Creates a function named 'a'

The statement assigns the value 10 to the variable named 'a'.

If you write x = 5; then x = 7;, what is the value of x?

A 7

B 5

C 12

D Error

The second assignment replaces the first, so x holds the value 7.

Which symbol is used to assign a value to a variable in MATLAB?

A :=

B ==

C =

D ->

The equal sign '=' is used for assignment in MATLAB.

What type of data does name = 'John'; store in the variable 'name'?

A Number

B Character array (text)

C Boolean

D Function

Text in single quotes is stored as a character array in MATLAB.

Explain how to create a variable and assign a value to it in MATLAB.

Think about the simple statement where you name something and give it a value.

What are the rules for naming variables in MATLAB?

Consider what characters are allowed and where the name can start.

Practice

1.

What does the following MATLAB code do?
x = 10;

easy

A. Creates a variable named x and assigns it the value 10

B. Creates a function named x with input 10

C. Deletes the variable x

D. Prints the number 10 on the screen

Solution

1. Step 1: Understand variable assignment syntax

   The code uses = to assign a value to a variable.

2. Step 2: Identify the variable and value

   Variable x is assigned the value 10.

3. Final Answer:

   Creates a variable named x and assigns it the value 10 -> Option A

4. Quick Check:

   Variable assignment = Creates variable with value [OK]

Hint: Look for '=' to spot variable assignment [OK]

Common Mistakes:

• Thinking '=' prints output
• Confusing variable creation with function definition
• Missing semicolon means output prints but variable still created

2.

Which of the following is the correct way to assign the value 5 to variable a in MATLAB?

easy

A. a == 5;

B. a = 5;

C. 5 = a;

D. a := 5;

Solution

1. Step 1: Recall MATLAB assignment operator

   MATLAB uses = to assign values to variables.

2. Step 2: Check each option

   a = 5; uses a = 5; which is correct syntax.

3. Final Answer:

   a = 5; -> Option B

4. Quick Check:

   Assignment uses '=' in MATLAB [OK]

Hint: Use single '=' for assignment, not '==' [OK]

Common Mistakes:

• Using '==' which is a comparison, not assignment
• Trying to assign value to a number (5 = a)
• Using ':=' which is not MATLAB syntax

3.

What is the value of variable y after running this code?

y = 3;
y = y + 4;

medium

A. 7

B. 3

C. 4

D. Error

Solution

1. Step 1: Assign initial value to y

   Variable y is first set to 3.

2. Step 2: Add 4 to current value of y

   New value is 3 + 4 = 7.

3. Final Answer:

   7 -> Option A

4. Quick Check:

   3 + 4 = 7 [OK]

Hint: Add numbers step-by-step to find final value [OK]

Common Mistakes:

• Thinking y stays 3 after addition
• Confusing assignment with comparison
• Expecting syntax error due to reuse of variable

4.

Identify the error in this MATLAB code:

1var = 10;

medium

A. Variable names cannot contain letters

B. Missing semicolon at the end

C. Assignment operator is wrong

D. Variable names cannot start with a number

Solution

1. Step 1: Check variable naming rules

   MATLAB variable names must start with a letter, not a number.

2. Step 2: Analyze given variable name

   Variable name 1var starts with '1', which is invalid.

3. Final Answer:

   Variable names cannot start with a number -> Option D

4. Quick Check:

   Variable names start with letters [OK]

Hint: Variable names must start with a letter [OK]

Common Mistakes:

• Thinking semicolon is mandatory for syntax
• Confusing assignment operator '=' with '=='
• Assuming numbers can start variable names

5.

You want to create two variables a and b where a is 5 and b is twice a. Which code correctly does this?

a = 5;
b = 2 * a;

hard

A. a = 5;b = a * a;

B. a = 5;b = 2 + a;

C. a = 5;b = 2 * a;

D. a = 5;b = a / 2;

Solution

1. Step 1: Assign value 5 to variable a

   Code a = 5; correctly assigns 5 to a.

2. Step 2: Assign b as twice a

   Code b = 2 * a; correctly calculates twice the value of a.

3. Final Answer:

   a = 5; b = 2 * a; -> Option C

4. Quick Check:

   b = 2 * a means b is double a [OK]

Hint: Multiply variable by 2 to get double value [OK]

Common Mistakes:

• Adding instead of multiplying for double
• Dividing instead of multiplying
• Multiplying variable by itself instead of 2