String searching (contains, strfind) in MATLAB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the contains function do in MATLAB?

The contains function checks if a string or array of strings contains a specified substring and returns a logical true or false.

beginner

How does strfind differ from contains in MATLAB?

strfind returns the starting indices of the substring within the string, while contains returns a logical value indicating presence or absence.

beginner

What is the output of strfind('hello world', 'o')?

It returns the indices where 'o' appears: [5 8].

intermediate

Can contains handle arrays of strings in MATLAB?

Yes, contains can check each element of a string array or cell array of character vectors and return a logical array.

beginner

What happens if strfind does not find the substring?

It returns an empty array [] indicating no matches.

What does contains('apple', 'p') return?

A true

B false

C [2 3]

D []

contains returns true if the substring is found anywhere in the string.

What is the output of strfind('banana', 'na')?

A [3 5]

B [2 4]

C [4 6]

D []

strfind returns the starting indices of each occurrence of 'na' in 'banana', which are positions 3 and 5.

If strfind does not find the substring, what does it return?

A 0

B false

C empty array []

D NaN

strfind returns an empty array [] when no match is found.

Which function returns a logical array when searching multiple strings?

A strfind

B contains

C find

D strcmp

contains returns a logical array indicating presence of the substring in each element.

What is the difference between contains and strfind?

A <code>contains</code> returns indices, <code>strfind</code> returns logical

B Both return logical arrays

C Both return indices

D <code>contains</code> returns logical, <code>strfind</code> returns indices

contains returns true/false, while strfind returns the starting positions of the substring.

Explain how to use contains to check if a substring exists in multiple strings.

Think about searching in a list of words.

Describe what strfind returns and how it can be used to find substring positions.

Imagine looking for where a word starts inside a sentence.