How to Replace Values in R with Examples

There are several ways to replace/update column values in R DataFrame. In this article, I will explain how to update data frame values of single/multiple/all columns by using the R base functions/notation and dplyr package.

1. Update Specified Data Frame Column Value

To replace a column value in R you can use square bracket notation df[], By using this you can update values on a single column or all columns. To refer to a single column you can use df$column_name. The following example updates Orange St with Portola Pkwy on the address column.


# Replace String with Another Stirng on a single column
df$address[df$address == 'Orange St'] <- 'Portola Pkwy'
df

Yields below output.

To update all column values use df[] notation. You can use df[df=="Portola Pkwy"] <- "Orange St" it to update all columns by replacing 'Portola Pkwy'(wherever present in the columns of the data frame) with 'orange St'.


# Replace String with Another String on All Columns
df[df=="Portola Pkwy"] <- "Orange St"
df

# Output
#   id        address work_address
# 1  1      Orange St      Main St
# 2  2     Anton Blvd         <NA>
# 3  3 Jefferson Pkwy   Apple Blvd
# 4 NA                   Orange St

Alternatively, you can use the str_replace() method from stringr the package to update the sub-string of a string(column value) with another sub-string in R DataFrame. The following code updates substring St with Street on the address column.


# Replace String with another String
library(stringr)
df$address <- str_replace(df$address, "St", "Street")
print(df)

# Output
#  id        address work_address
# 1  1  Orange Street      Main St
# 2  2     Anton Blvd         <NA>
# 3  3 Jefferson Pkwy   Apple Blvd
4 NA                   Orange St

2. Replace with Another Column Value

In R replacing a column value with another column is the most used example, let’s say you want to apply some calculation on the existing column and update the result on the same column, this can be achieved with the below R example.

Here I am multiplying column id with the number 5 and assigning the result to the same id column. Similarly, you can also assign the result to another column.


# Create new column from existing column
df['id'] <- df['id'] * 5
df

# Output
#  id        address work_address
# 1  5  Orange Street      Main St
# 2 10     Anton Blvd         <NA>
# 3 15 Jefferson Pkwy   Apple Blvd
# 4 NA                   Orange St

3. Update Based on Condition

In case you want to replace column values based on a condition, you need to check with the condition and assign the value from another column to this column when the condition matches. The below example updates the address column with the value of work_address when only if the address value is 'Orange Street'.


# Replace column value with another based on condition
df$address[df$address == 'Orange Street'] <- df$work_address
df

# Output
#  id        address work_address
# 1  5        Main St      Main St
# 2 10     Anton Blvd         <NA>
# 3 15 Jefferson Pkwy   Apple Blvd
# 4 NA                   Orange St

4. Using dplyr Package

Similarly, you can use mutate() function from dplyr package to change column values, dplyr is a third-party package hence, you need to load the library using library("dplyr") to use its methods. In case you don’t have this package, install it using install.packages("dplyr").

For bigger data sets it is best to use the methods from the dplyr package as they perform 30% faster. This package uses C++ code to evaluate.


# Using dplyr package
library(dplyr)    
df <- df %>% 
   mutate(address = ifelse(address == '',work_address,address))
df

Yields below output.


# Output
  id        address work_address
1  5  Orange Street      Main St
2 10     Anton Blvd         <NA>
3 15 Jefferson Pkwy   Apple Blvd
4 NA      Orange St    Orange St

5. Update Missing Values with Empty/Blank String

NA values are considered as missing values, to replace these missing (NA) values with empty strings use the below example. Here, the is.na() function checks if a column value is NA, if yes then it updates it with an empty string. Similarly, you can also replace empty string with NA values.


#Replace na values with blank using is.na()
df[is.na(df)] <- ""
df

# Output
#  id        address work_address
# 1  5        Main St      Main St
# 2 10     Anton Blvd             
# 3 15 Jefferson Pkwy   Apple Blvd
# 4         Orange St     Orange St

6. Update Missing Values with 0

Replacing all missing values with an empty string is not a good approach as you may have integer values and an empty string is not the right thing to use. So to replace NA with 0 on integer columns use the below approach.


# Replace only numeric columns
library("tidyr")
library("dplyr")

df <- df %>% 
    mutate_if(is.numeric, ~replace_na(., 0))

7. Complete Example of Update Column Values


# Create dataframe
df <- data.frame(id=c(1,2,3,NA),
          address=c('Orange St','Anton Blvd','Jefferson Pkwy',''),
          work_address=c('Main St',NA,'Apple Blvd','Portola Pkwy'))

df

# Replace String with Another Stirng on a single column
df$address[df$address == 'Orange St'] <- 'Portola Pkwy'
df

# Replace String with Another String on All Columns
df[df=="Portola Pkwy"] <- "Orange St"
df

# Replace String with another String
library(stringr)
df$address <- str_replace(df$address, "St", "Street")
print(df)

# Create new column from existing column
df['id'] <- df['id'] * 5
df

# Replace column value with another based on condition
df$address[df$address == 'Orange Street'] <- df$work_address
df

# Using dplyr package
library(dplyr)    
df <- df %>% 
   mutate(address = ifelse(address == '',work_address,address))
df

#Replace na values with blank using is.na()
df[is.na(df)] <- ""
df

Frequently Asked Questions of Replace Values in R with Examples

How do I replace specific values in a vector or data frame in R?

Use the df[] notation or logical conditions to replace the specified values with new values in an R data frame. For example, df$column_name[df$column_name == 'old_col_value'] <- 'new_col_value'

How can I replace missing values (NA) in my data with a specific value?

Use is.na() to identify missing values and replace them with a desired value. For example, df[is.na(df)] <- 0

How is it possible to replace multiple values at once?

Using %in% or other logical conditions to replace multiple values simultaneously. For example,
vec <- c(1, 2, 3, 4, 5) <br/>vec %in% c(2, 4) <- 0

8. Conclusion

In this article, you have learned how to replace/update data frame values of single/multiple/all columns by using the R base functions/notation, and the dplyr package with well-defined examples.

References

https://www.rdocumentation.org/packages/base/versions/3.6.2/topics/replace