For loops in MATLAB - Step-by-Step Execution

Concept Flow - For loops

Initialize loop variable i = start

↓

Check: i <= end?

No→EXIT loop

Yes↓

Execute loop body

↓

Update i = i + step

↩Back to Check

The loop starts by setting a variable, checks if it meets the condition, runs the code inside if yes, then updates the variable and repeats until the condition is false.

Execution Sample

MATLAB

for i = 1:3
    disp(i)
end

This loop prints numbers 1, 2, and 3 one by one.

Execution Table

Iteration	i value	Condition (i <= 3)	Action	Output
1	1	true	Display i	1
2	2	true	Display i	2
3	3	true	Display i	3
4	4	false	Exit loop

💡 i reaches 4, condition 4 <= 3 is false, loop ends

Variable Tracker

Variable	Start	After 1	After 2	After 3	Final
i	1	2	3	4	4

Key Moments - 3 Insights

Why does the loop stop after i = 3 and not continue?

Because the condition i <= 3 becomes false when i is 4, as shown in the last row of the execution table where the loop exits.

Does the loop body run when the condition is false?

No, the loop body only runs when the condition is true. The execution table shows the loop exits immediately when the condition is false at iteration 4.

What happens to the variable i after the loop ends?

The variable i becomes 4 after the last update, which caused the loop to stop, as tracked in the variable tracker.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of i during the 2nd iteration?

A 2

B 3

C 1

D 4

💡 Hint

Check the 'i value' column in the execution table at iteration 2.

At which iteration does the loop condition become false?

A 3

B 1

C 4

D 2

💡 Hint

Look at the 'Condition' column in the execution table where it changes to false.

If the loop was changed to for i = 1:4, how many times would the loop body run?

A 3 times

B 4 times

C 5 times

D 1 time

💡 Hint

The loop runs once for each value of i from start to end, inclusive, as shown in the variable tracker.

Concept Snapshot

for i = start:end
    % code to repeat
end
- Loop runs from start to end values
- Executes code inside for each i
- Stops when i exceeds end
- i updates automatically each iteration

Full Transcript

This visual shows how a for loop in MATLAB works. The loop starts by setting i to 1. It checks if i is less than or equal to 3. If yes, it runs the code inside, here displaying i. Then i increases by 1. This repeats until i becomes 4, which fails the condition, so the loop stops. The variable tracker shows i's value at each step. The key moments clarify common confusions like why the loop stops and when the body runs. The quiz tests understanding of i's values and loop stopping conditions.