String replacement in MATLAB - Step-by-Step Execution

Concept Flow - String replacement

Start with original string

↓

Identify substring to replace

↓

Find all occurrences

↓

Replace each occurrence with new substring

↓

Return modified string

↓

End

The program starts with an original string, finds all parts matching the target substring, replaces them with a new substring, and returns the updated string.

Execution Sample

MATLAB

str = "Hello world!";
newStr = replace(str, "world", "MATLAB");
disp(newStr);

This code replaces the word "world" with "MATLAB" in the string and displays the result.

Execution Table

Step	Action	Input String	Substring to Replace	Replacement Substring	Resulting String
1	Start	Hello world!	world	MATLAB	Hello world!
2	Find substring 'world'	Hello world!	world	MATLAB	Found at position 7
3	Replace 'world' with 'MATLAB'	Hello world!	world	MATLAB	Hello MATLAB!
4	Display result	Hello MATLAB!	world	MATLAB	Hello MATLAB!

💡 All occurrences of 'world' replaced; execution ends.

Variable Tracker

Variable	Start	After Step 2	After Step 3	Final
str	"Hello world!"	"Hello world!"	"Hello world!"	"Hello world!"
newStr	undefined	undefined	"Hello MATLAB!"	"Hello MATLAB!"

Key Moments - 2 Insights

Why does the original string 'str' not change after replacement?

In MATLAB, the replace function returns a new string with replacements; it does not modify the original string variable 'str' (see execution_table step 3 and variable_tracker).

What happens if the substring to replace is not found?

If the substring is not found, the replace function returns the original string unchanged, so no replacement occurs (not shown in this example but implied by step 2).

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of newStr after step 3?

A "Hello world!"

B "MATLAB world!"

C "Hello MATLAB!"

D "Hello!"

💡 Hint

Check the 'Resulting String' column in execution_table row for step 3.

At which step does the program find the substring to replace?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look at the 'Action' column in execution_table to find when substring is located.

If the substring to replace was 'hello' (lowercase), what would happen?

A No replacement would happen because 'hello' does not match 'Hello' exactly.

B An error would occur.

C The replacement would still happen because replace is case-insensitive.

D The entire string would be replaced.

💡 Hint

MATLAB's replace function is case-sensitive; check variable_tracker and execution_table for case matching.

Concept Snapshot

String replacement in MATLAB:
Use replace(originalString, oldSubstring, newSubstring)
Returns a new string with all occurrences of oldSubstring replaced
Original string remains unchanged
Case-sensitive matching
Useful for simple text substitutions

Full Transcript

This example shows how MATLAB replaces parts of a string. We start with the string 'Hello world!'. The program looks for the substring 'world'. It finds it starting at position 7. Then it replaces 'world' with 'MATLAB', creating a new string 'Hello MATLAB!'. The original string stays the same. Finally, the new string is displayed. This process helps change text inside strings without altering the original data.