Built-in Character Functions in R

In earlier tutorials we have seen that how to create character vector in R which contains character strings. To manipulate strings or character vectors, R has many built in functions for characters.

Function	Description
`nchar()`	Get the length of string
`toupper(x)`	Convert to Upper case
`tolower(x)`	Convert to Lower case
`casefold()`	case folding
`chartr()`	Character translation in character vector
`substr(x,start=n1,stop=n2)`	Extract or replace sub-strings in a character vector
`strsplit()`	Split the character vector
`strrep()`	Repeat the character string
`paste()`	Concatenate vectors after converting to character

Examples of Character Functions

Let us discuss how to use all the above built-in character functions in R with the help of examples.

String Length in R

The number of characters (including space) in a string or elements of character vector can be counted using nchar() function.

# create a string
x <- "R Programming"
# count the number of characters
nchar(x)

[1] 13

# count the number of elements
length(x)

[1] 1

# create a character vector
y <-c("One","Two","Three","Four","Five")
# count no. of letters in each element of y
nchar(y)

[1] 3 3 5 4 4

# count the number of elements in y
length(y)

[1] 5

Note than the length() function gives the number of elements in a vector and nchar() function gives the number of characters in each element of a vector.

toupper() function in R

Many times, during programming we need to change the case of a string or character. The toupper() function converts the letters in a given string to uppercase.

x <- "r programming"
toupper(x)

[1] "R PROGRAMMING"

tolower() function in R

The tolower() function converts the letters in a given string to lowercase.

y <- 'R Programming'
tolower(y)

[1] "r programming"

casefold() function in R

By default the casefold() function converts all the characters to lower case. But we can use the argument upper=TRUE to convert all the characters to upper case.

casefold("R is The bEst ProGramminG LanGuagE")

[1] "r is the best programming language"

casefold("R is The bEst ProGramminG LanGuagE", upper=TRUE)

[1] "R IS THE BEST PROGRAMMING LANGUAGE"

chartr() function in R

The chartr(old,new,x) function is used to translate the old characters to new characters in character vectors x

Suppose we need to translate the letter "r" with "R" in the sentence "r Language".

x <- "r Language"
chartr("r","R",x)

[1] "R Language"

The chartr() can also be used for multiple replacement.
Suppose we have x as R Programming Language and we need to translate all the character from the range m to p (i.e., m, n, o, p) in x to M to P (i.e., M, N, O, P) and g to G.

x <- "R Programming Language"
chartr("m-pg","M-PG", x)

[1] "R PrOGraMMiNG LaNGuaGe"

substr() function in R

The substr() function is used to extract or replace substrings in a character vector.

x <-  "R Programming"
substr(x,3,9) # extract

[1] "Program"

In the above example, R will extract a string from $3^{rd}$ letter to $9^{th}$ letter form x.

# Replace 3rd to 5th character by abc
substr(x,3,5)<-"abc" 
x

[1] "R abcgramming"

In the above example, R will replace $3^{rd}$ to $5^{th}$ character by the string abc.

strsplit() function in R

The strsplit(x, " ") function

x <-  c("R Programming","Python Programming")
strsplit(x," ")

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

[[2]]
[1] "Python"      "Programming"

strrep() function in R

The strrep(x,times) function repeat the character string in a character vector a given number of times.

strrep("ABC",4)

[1] "ABCABCABCABC"

Above command create a character string in which the string "ABC" is repeated four times.

strrep(c("X","Y","Z"),1:4)

[1] "X"    "YY"   "ZZZ"  "XXXX"

Above command create a vector containing the elements "X", "YY","ZZ" and "XXXX". Since the string contains less number of elements that the number of times, R will use recycling rule.

strrep("  ",1:3)

[1] "  "     "    "   "      "

Above function create vector with the given number of spaces. First element contain two spaces, second element contains four spaces and third element contains six spaces.

paste() function in R

The basic syntax of paste() function is

paste(..., sep=" ",collapse=NULL)

One of the most important function that can be used to create and build strings is the paste() function.

The paste() function takes one or more R objects and convert them to a character. After that it concatenates these characters to create one or more character string.

D <- c("R", "Python")
paste("Best programming language for data science is ",D)

[1] "Best programming language for data science is  R"     
[2] "Best programming language for data science is  Python"

paste("Treatment",1:3,sep="-")

[1] "Treatment-1" "Treatment-2" "Treatment-3"

Note than if the objects are of different length in paste function, R apply the recycling rule.

paste("Block",1:4,sep=" ")

[1] "Block 1" "Block 2" "Block 3" "Block 4"

Endnote

In this tutorial you learned anout some important character built-in functions available in R with illustration.

To learn more about other built-in functions and user-defined functions in R, please refer to the following tutorials:

Hope you enjoyed learning this tutorial on built-in character functions in R.