How to use map with str_replace_all for multiple pattern replacements

user_9394364 0
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I have a string and would like to capitalize two lowercase words. The following accomplishes what I want:

library(tidyverse)

"this is a test" %>% 
  str_replace_all("this", toupper("this")) %>% 
  str_replace_all("test", toupper("test"))

However, I would like to do this in a more efficient way as I have a lot of patterns to replace and do not want a separate line per pattern. I thought about using map, however I cannot get it to execute properly as the code below throws an error:

"this is a test" %>% 
  c("this", "test") %>% 
  map_chr(~str_replace_all(.x, toupper(.x)))

Can anyone tell me how to accomplish this?

r regex string
4 Answers

In regex, you can use \\U to change the capture group to upper case. Use | to separate different patterns.

val <- c("this", "test")
string <- "this is a test"

gsub(sprintf('(%s)', paste0(val, collapse = '|')), '\\U\\1', string, perl = TRUE)
#[1] "THIS is a TEST"

To answer your question you can use for loop to achieve the result that you are looking for.

for(i in val) {
  string <- stringr::str_replace_all(string, i, toupper(i))   
}

map/lapply does not have "knowledge" about the changes which happen in the middle hence it works on the same input.

user_39629140

In tidyverse, we may use reduce to do this

library(stringr)
library(purrr)
reduce(val, ~ str_replace_all(.x, .y, toupper(.y)), .init = string)
[1] "THIS is a TEST"

data

val <- c("this", "test")
string <- "this is a test"
user_37322710

Here's an alternative method packaged up into a function.

> SomeToUpper <- function(string_all, word_vector){
+   return(paste(
+     sapply(
+       unlist(str_split(string_all, " ")),
+       function(word){ 
+         ifelse(
+           word %in% word_vector, 
+           str_to_upper(word), 
+           word)}),
+     collapse = " ")
+   )
+ }
> SomeToUpper("this is a test", c("this", "test"))
[1] "THIS is a TEST"
user_102912910

Another recursion method using Reduce + gsub

> Reduce(
+   function(x, p) gsub(paste0("(", p, ")"), "\\U\\1", x, perl = TRUE),
+   val,
+   string
+ )
[1] "THIS is a TEST"
user_121587570
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