Strings in R

 

Strings in R

Introduction

A string is a sequence of characters enclosed within single quotes (' ') or double quotes (" "). Strings are used to store and manipulate textual data such as names, addresses, and messages.

In R, strings belong to the character data type.

Examples:

"Hello"
'R Programming'
"Computer Science"

Creating Strings

Strings can be created using either single or double quotes.

str1 <- "Hello"
str2 <- 'R Programming'

print(str1)
print(str2)

Output

[1] "Hello"
[1] "R Programming"

Character Vectors

Strings can be stored as vectors.

names <- c("John", "Mary", "Alex")

print(names)

Output

[1] "John" "Mary" "Alex"

Determining the Data Type

class()

str <- "Computer"

print(class(str))

Output

[1] "character"

typeof()

print(typeof(str))

Output

[1] "character"

String Functions

1. nchar()

Returns the number of characters in a string.

Syntax

nchar(string)

Example

str <- "Computer"

print(nchar(str))

Output

[1] 8

2. paste()

Concatenates strings with a separator.

Syntax

paste(string1, string2, sep=" ")

Example

first <- "R"
second <- "Programming"

result <- paste(first, second)

print(result)

Output

[1] "R Programming"

Using a Custom Separator

paste("2025", "06", "13", sep="-")

Output

[1] "2025-06-13"

3. paste0()

Concatenates strings without spaces.

Example

paste0("R", "Programming")

Output

[1] "RProgramming"

4. toupper()

Converts characters to uppercase.

str <- "Computer Science"

print(toupper(str))

Output

[1] "COMPUTER SCIENCE"

5. tolower()

Converts characters to lowercase.

str <- "Computer Science"

print(tolower(str))

Output

[1] "computer science"

6. substr()

Extracts a substring.

Syntax

substr(string, start, stop)

Example

str <- "Programming"

print(substr(str, 1, 4))

Output

[1] "Prog"

7. substring()

str <- "Programming"

print(substring(str, 5))

Output

[1] "ramming"

8. strsplit()

Splits a string into smaller strings.

Example

str <- "R Programming Language"

words <- strsplit(str, " ")

print(words)

Output

[[1]]
[1] "R"          "Programming" "Language"

9. grep()

Searches for patterns and returns indices.

Example

names <- c("John", "Alex", "Alice", "Mary")

print(grep("^A", names))

Output

[1] 2 3

10. grepl()

Returns TRUE or FALSE.

names <- c("John", "Alex", "Alice", "Mary")

print(grepl("^A", names))

Output

[1] FALSE TRUE TRUE FALSE

11. sub()

Replaces the first occurrence of a pattern.

Example

str <- "banana"

print(sub("a", "A", str))

Output

[1] "bAnana"

12. gsub()

Replaces all occurrences.

str <- "banana"

print(gsub("a", "A", str))

Output

[1] "bAnAnA"

13. sprintf()

Formats strings.

Example

name <- "John"
age <- 20

msg <- sprintf("Name = %s, Age = %d", name, age)

print(msg)

Output

[1] "Name = John, Age = 20"

String Comparison

str1 <- "Apple"
str2 <- "Banana"

print(str1 == str2)

Output

[1] FALSE

Lexicographic Comparison

print("Apple" < "Banana")

Output

[1] TRUE

Converting Strings

Character to Numeric

str <- "100"

num <- as.numeric(str)

print(num)

Output

[1] 100

Numeric to Character

num <- 25

str <- as.character(num)

print(str)

Output

[1] "25"

Escape Sequences

SequenceMeaning
\nNew line
\tTab
\\Backslash
\"Double quote
\'Single quote

Example

cat("Hello\nWorld")

Output

Hello
World

Common String Operations

Reverse a String

str <- "HELLO"

chars <- strsplit(str, "")[[1]]

rev_str <- paste(rev(chars), collapse="")

print(rev_str)

Output

[1] "OLLEH"

Count Vowels

str <- "Computer Science"

chars <- strsplit(tolower(str), "")[[1]]

count <- 0

for(ch in chars)
{
    if(ch %in% c("a","e","i","o","u"))
        count <- count + 1
}

print(count)

Output

[1] 6

Check Palindrome

str <- "madam"

chars <- strsplit(str, "")[[1]]

rev_str <- paste(rev(chars), collapse="")

if(str == rev_str)
    print("Palindrome")
else
    print("Not Palindrome")

Output

[1] "Palindrome"

Another Method

str <- readline("Enter a string:")
rstr=""
for ( i in nchar(str):1)
{
  rstr=paste0(rstr,substr(str,i,i))
}
if (str==rstr)
  cat ("pal\n") else
cat ("not pal\n")

Useful String Functions Summary

FunctionPurpose
nchar()    Length of string
paste()    Concatenate strings
paste0()    Concatenate without spaces
toupper()    Convert to uppercase
tolower()    Convert to lowercase
substr()    Extract substring
substring()    Extract substring
strsplit()    Split string
grep()    Pattern matching
grepl()    Returns TRUE/FALSE
sub()    Replace first occurrence
gsub()    Replace all occurrences
sprintf()    Format strings

Applications of Strings

  • Processing names and addresses.
  • Pattern matching and searching.
  • Text formatting.
  • Parsing files and documents.
  • Natural language processing.
  • Data cleaning and preprocessing.

Conclusion

Strings are fundamental data structures used to store and manipulate textual information in R. R provides a rich set of built-in functions for string creation, concatenation, searching, extraction, replacement, and formatting. Mastery of string operations is essential for data preprocessing, text analytics, and general-purpose programming.

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