Replace letter in array in specific way

user_12267227 0
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I have these vectors:

 texts=c("AANAAA","NNAAAA","AAAAAA", "NAAANN")

 letter=c("C","C","G","T","P","D")

I am trying to replace N for each element in texts and replace it with a character from second array letter by position.

Take "AANAAA", the N at third position should be replaced by the third element of letter, i.e. G

My expected output is:

texts=c("AAGAAA","CCAAAA","AAAAAA", "CAAAPD")

I was trying gsub and a for loop

for (i in 1:6) {
   for (j in 1:4)
      gsub("N",letter[i],texts[j][i])
}

but it didn't work.

r regex string
3 Answers

You can do that in base R like this. No loop is required. gregexpr extracts a list of positions in texts where matched. We then replace characters at those positions with corresponding characters in letter using regmatches<-.

 m <- gregexpr("N", texts, fixed = TRUE)
 regmatches(texts, m) <- lapply(m, \(i, x) x[i], letter)

Output

>  texts 
[1] "AAGAAA" "CCAAAA" "AAAAAA" "CAAAPD"
user_108024990

Using loops, split texts into letters and replace "N" with corresponding letter:

sapply(strsplit(texts, ""), function(i){
  ix <- which(i == "N")
  i[ ix ] <- letter[ ix ]
  paste(i, collapse = "")
})
# [1] "AAGAAA" "CCAAAA" "AAAAAA" "CAAAPD"
user_6800680

A solution based on tidyverse/purrr:

library(tidyverse)

texts=c("AANAAA","NNAAAA","AAAAAA", "NAAANN")
letter=c("C","C","G","T","P","D")

texts %>% 
  map(~ str_split(.x, "") %>% unlist %>% 
        map2_chr(letter, ~ if_else(.x == "N", .y, .x))) %>% 
  map_chr(~ str_c(.x, collapse = ""))

#> [1] "AAGAAA" "CCAAAA" "AAAAAA" "CAAAPD"
user_115644870
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