Renaming columns in a data frame

Problem

You want to rename the columns in a data frame.

Solution

Start with a sample data frame with three columns:

  1. d <- data.frame(alpha=1:3, beta=4:6, gamma=7:9)
  2. d
  3. #>   alpha beta gamma
  4. #> 1     1    4     7
  5. #> 2     2    5     8
  6. #> 3     3    6     9
  8. names(d)  
  9. #> [1] "alpha" "beta"  "gamma"

The simplest way is to use rename() from the plyr package:

  1. library(plyr)
  2. rename(d, c("beta"="two", "gamma"="three"))
  3. #>   alpha two three
  4. #> 1     1   4     7
  5. #> 2     2   5     8
  6. #> 3     3   6     9

If you don’t want to rely on plyr, you can do the following with R’s built-in functions. Note that these modify d directly; that is, you don’t have to save the result back into d.

  1. # Rename column by name: change "beta" to "two"
  2. names(d)[names(d)=="beta"] <- "two"
  3. d
  4. #>   alpha two gamma
  5. #> 1     1   4     7
  6. #> 2     2   5     8
  7. #> 3     3   6     9
  9. # You can also rename by position, but this is a bit dangerous if your data
  10. # can change in the future. If there is a change in the number or positions of
  11. # columns, then this can result in wrong data.
  13. # Rename by index in names vector: change third item, "gamma", to "three"
  14. names(d)[3] <- "three"
  15. d
  16. #>   alpha two three
  17. #> 1     1   4     7
  18. #> 2     2   5     8
  19. #> 3     3   6     9

It’s also possible to use R’s string search-and-replace functions to rename columns. Note that the ^ and $ surrounding alpha are there to ensure that the entire string matches. Without them, if there were a column named alphabet, it would also match, and the replacement would be onebet.

  1. names(d) <- sub("^alpha$", "one", names(d))
  2. d
  3. #>   one two three
  4. #> 1   1   4     7
  5. #> 2   2   5     8
  6. #> 3   3   6     9
  8. # Across all columns, replace all instances of "t" with "X"
  9. names(d) <- gsub("t", "X", names(d))
  10. d
  11. #>   one Xwo Xhree
  12. #> 1   1   4     7
  13. #> 2   2   5     8
  14. #> 3   3   6     9
  16. # gsub() replaces all instances of the pattern in each column name.
  17. # sub() replaces only the first instance in each column name.