How to Reverse a string in R

Question

I\'m trying to teach myself R and in doing some sample problems I came across the need to reverse a string.

Here\'s what I\'ve tried so far but the paste operation d

Answer 1

You can do with rev() function as mentioned in a previous post.

`X <- "MyString"

RevX <- paste(rev(unlist(strsplit(X,NULL))),collapse="")

Output : "gnirtSyM"

Thanks,

Answer 2

You can also use the IRanges package.

library(IRanges)
x <- "ATGCSDS"
reverse(x)
# [1] "SDSCGTA"

You can also use the Biostrings package.

library(Biostrings)
x <- "ATGCSDS"
reverse(x)
# [1] "SDSCGTA"

Answer 3

The easiest way to reverse string:

#reverse string----------------------------------------------------------------
revString <- function(text){
  paste(rev(unlist(strsplit(text,NULL))),collapse="")
}

#example:
revString("abcdef")

Answer 4

##function to reverse the given word or sentence

reverse <- function(mystring){ 
n <- nchar(mystring)
revstring <- rep(NA, n)
b <- n:1
c <- rev(b)
for (i in 1:n) {
revstring[i] <- substr(mystring,c[(n+1)- i], b[i])
 }
newrevstring <- paste(revstring, sep = "", collapse = "")
return (cat("your string =", mystring, "\n",
("reverse letters = "), revstring, "\n", 
"reverse string =", newrevstring,"\n"))
}

Answer 5

Here's a solution with gsub. Although I agree that it's easier with strsplit and paste (as pointed out in the other answers), it may be interesting to see that it works with regular expressions too:

test <- "greg"

n <- nchar(test) # the number of characters in the string

gsub(paste(rep("(.)", n), collapse = ""),
     paste("", seq(n, 1), sep = "\\", collapse = ""),
     test)

# [1] "gerg"

Answer 6

stringi has had this function for quite a long time:

stringi::stri_reverse("abcdef")
## [1] "fedcba"

Also note that it's vectorized:

stringi::stri_reverse(c("a", "ab", "abc"))
## [1] "a"   "ba"  "cba"