Convert Character to Factor in R (With Examples)

We can use the following syntax to convert a character vector to a factor vector in R:

factor_vector <- as.factor(character_vector)

This tutorial provides several examples of how to use this function in practice.

Example 1: Convert a Vector from Character to Factor

The following code shows how to convert a character vector to a factor vector:

#create character vector
character_vector <- c('First', 'Second', 'Third')

#convert character vector to factor vector
factor_vector <- as.factor(character_vector)

#view factor vector
factor_vector

[1] First  Second Third 
Levels: First Second Third

#confirm class of factor vector
class(factor_vector)

[1] "factor"

Example 2: Convert a Column from Character to Factor

The following code shows how to convert a specific column in a data frame from character to factor:

#create data frame
df <- data.frame(a = c('12', '14', '19', '22', '26'),
                 b = c(28, 34, 35, 36, 40))

#convert column 'a' from character to factor
df$a <- as.factor(df$a)

#view new data frame
df

       a  b
1  First 28
2 Second 34
3  Third 40

#confirm class of factor vector
class(df$a)

[1] "factor"

Example 3: Convert Several Columns from Character to Factor

The following code shows how to convert all character columns in a data frame from character to factor:

#create data frame
df <- data.frame(a = c('12', '14', '19', '22', '26'),
                 b = c('28', '34', '35', '36', '40'),
                 c = as.factor(c(1, 2, 3, 4, 5)),
                 d = c(45, 56, 54, 57, 59))

#display classes of each column
sapply(df, class)

          a           b           c           d 
"character" "character"    "factor"   "numeric" 

#convert all character columns to factor
df <- as.data.frame(unclass(df), stringsAsFactors = TRUE)

#display classes of each column
sapply(df, class)

        a         b         c         d 
 "factor"  "factor"  "factor" "numeric" 

This code made the following changes to the data frame columns:

• Column a: From character to factor
• Column b: From character to factor
• Column c: Unchanged (since it was already a factor)
• Column d: Unchanged (since it was numeric)

By using the and functions, we were able to convert only the character columns to factor columns and leave all other columns unchanged.

Additional Resources