For loops in MATLAB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple for loop with indexing

What is the output of the following MATLAB code?

MATLAB

sumVal = 0;
for i = 1:4
    sumVal = sumVal + i;
end
sumVal

A 10

B 24

C 0

D Error: Undefined variable 'sumVal'

💡 Hint

Think about adding numbers from 1 to 4 step by step.

The loop adds 1 + 2 + 3 + 4 which equals 10.

❓ Predict Output

intermediate

For loop with decrementing index

What will be the value of variable 'result' after running this code?

MATLAB

result = 1;
for k = 5:-1:2
    result = result * k;
end

A 120

B 20

C Error: Invalid for loop range

D 1

💡 Hint

Multiply numbers from 5 down to 2.

The loop multiplies 5*4*3*2 = 120.

🔧 Debug

advanced

Identify the error in this for loop

What error does this MATLAB code produce?

MATLAB

total = 0;
for i = 1 5
    total = total + i;
end

A Syntax error: Missing 'end' statement

B Runtime error: Variable 'total' undefined

C No error, output is 15

D Syntax error: Missing colon in for loop range

💡 Hint

Check the for loop range syntax carefully.

The for loop range must use a colon (1:5), not a space.

❓ Predict Output

advanced

Nested for loops output

What is the value of 'count' after running this nested loop?

MATLAB

count = 0;
for i = 1:3
    for j = 1:2
        count = count + 1;
    end
end

A 5

B 6

C 3

D 2

💡 Hint

Multiply the number of iterations of both loops.

Outer loop runs 3 times, inner loop 2 times, total 3*2=6 increments.

🧠 Conceptual

expert

Effect of modifying loop variable inside for loop

Consider this MATLAB code. What is the final value of 'x' after the loop finishes?

MATLAB

x = 0;
for i = 1:4
    x = x + i;
    i = 10;
end

A 11

B 9

C 10

D 20

💡 Hint

Changing the loop variable inside the loop does not affect the iteration.

The loop variable 'i' is controlled by the for loop and resetting it inside does not change the sequence. So x sums 1+2+3+4=10.