nchar and substring in R Programming - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the nchar() function do in R?

It returns the number of characters in a string, including spaces and special characters.

beginner

How do you extract a part of a string in R?

You use the substring() function, specifying the start and end positions of the part you want.

beginner

Example: What is the output of nchar("Hello World")?

The output is 11 because there are 11 characters including the space.

beginner

Example: What does substring("Programming", 2, 5) return?

It returns "rogr", which are characters from position 2 to 5.

intermediate

Can substring() extract from the middle to the end of a string without specifying the end?

Yes, if you omit the end position, it extracts from the start position to the end of the string.

What does nchar("R is fun") return?

A 7

B 8

C 9

D 6

The string "R is fun" has 8 characters including spaces.

What is the result of substring("Data", 2, 3)?

A "at"

B "Da"

C "ta"

D "a"

Characters at positions 2 and 3 are "a" and "t", so the result is "at".

If you want to get the last 3 characters of a string "Example", which is the correct call?

A substring("Example", 6, 8)

B substring("Example", 4, 7)

C substring("Example", 5, 7)

D substring("Example", 5)

Positions 5 to 7 correspond to the last 3 characters "ple".

What happens if substring() start position is greater than string length?

A Returns empty string

B Returns whole string

C Returns error

D Returns NULL

If start position is beyond string length, substring returns an empty string.

Which function would you use to find how many characters are in a string?

A substring()

B str_length()

C length()

D nchar()

nchar() returns the number of characters in a string.

Explain how to use nchar() and substring() to find the length of a string and extract a part of it.

Think about counting letters and cutting out a piece of a word.

Describe what happens if you use substring() with only a start position and no end position.

Imagine cutting a string from a point to the end.