Question

I need to write a generic function for “find and replace in R”. How can I write a function that takes the following inputs

• A CSV file (or data frame)
• A string to find, for example “[e-mail]”
• A string the replace the found string with, for example “medium”

and rewrites the CSV file/data frame so that all the found strings are replaced with the replacement string?

Answer 1

Here’s a quick function to do the job:

library(stringr)

replace_all <- function(df, pattern, replacement) {
  char <- vapply(df, function(x) is.factor(x) || is.character(x), logical(1))
  df[char] <- lapply(df[char], str_replace_all, pattern, replacement)  
  df
}

replace_all(iris, "setosa", "barbosa")

Basically, it identifies all the variables in the data frame that are characters or factors, and then applies str_replace_all to each column. Pattern should be a regular expression, but if you want to match a fixed string, you can do (e.g.)

replace_all(iris, fixed("setosa"), "barbosa")