capitalize last letter of a single word

Question

In R trying to write a function that takes the word MarsuPial and results in marsupiaL.

current code

mycap <- function(mystr = "") {
  mystr <- tolower(mystr)
  a <- substr(mystr, 1, 1)
  b <- substr(mystr, 2, nchar(mystr))
  paste(tolower(a), b, sep = "")
}

some other options `gsub('(.*)(.)$', '\\L\\1\\U\\2', 'MarsuPial', perl = TRUE)` or `gsub('(.)$', '\\U\\1', tolower('MarsuPial'), perl = TRUE)` — rawr, Aug 04 '20 at 02:16
@rawr I like your solution - `myCap <- function(x) sub('(.*)(.)$', '\\L\\1\\U\\2', x, perl = TRUE)` seems to be the fastest of the bunch (not that it would matter in most cases) — user12728748, Aug 04 '20 at 02:35

score 1 · Accepted Answer · answered Aug 04 '20 at 02:14

1

You can use substr<- to capitalise the last character.

mycap <- function(mystr = "") {
  mystr <- tolower(mystr)
  n <- nchar(mystr)
  substr(mystr, n, n) <- toupper(substr(mystr, n, n))
  return(mystr)
}

mycap('MarsuPial')
#[1] "marsupiaL"
mycap('dummy')
#[1] "dummY"

answered Aug 04 '20 at 02:14

Ronak Shah

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That's what I was looking for! Thank you! – putnro01 Aug 04 '20 at 02:18

score 1 · Answer 2 · answered Aug 04 '20 at 02:14

mycap <- function(mystr = "") {
  # a: the string without the last character
  a <- substr(mystr, 1, nchar(mystr)-1)

  # b: only the last character 
  b <- substr(mystr, nchar(mystr), nchar(mystr))

  # lower(a) and upper(b)
  paste(tolower(a), toupper(b), sep = "")
}

For your example:

mycap("MarsuPial")
[1] "marsupiaL

Maurits Evers · Answer 3 · 2020-08-04T04:21:02.653

Another option avoiding string subsetting/splitting is to convert the string to an integer vector to reverse the order so that we can use stringr::str_to_title.

library(stringr)
library(dplyr)
mycap <- function(mystr = "") {
    mystr %>% utf8ToInt %>% rev %>% intToUtf8 %>% str_to_title %>% utf8ToInt %>% rev %>% intToUtf8
}

mycap("MarsuPial")
#[1] "marsupiaL"
mycap("dummy")
#[1] "dummY"

Or another fast option is to use stringi::stri_reverse and stringi::stri_trans_totitle

library(stringi)
mycap <- function(mystr = "") stri_reverse(stri_trans_totitle(stri_reverse(mystr)))

capitalize last letter of a single word

3 Answers3