R/left_and_right.R

In emilelatour/lamisc: Latour's Little Helpers

#' @title
#' Return text to the left and the right of a string
#'
#' @description
#' `left` takes a string and a character as arguments, then returns the
#' characters to the left. `right` takes a string and a character as
#' arguments, then returns the characters to the right.
#'
#' Wrappers around some regular expressions. `Left` and `right` operate
#' similar to combining `left()`/`right()` and `search()` in excel. So maybe
#' there's a bit of nostalgia for me in using these functions. But I also
#' think that the naming makes it clearer what is going on.
#'
#' @references
#' \url{https://stackoverflow.com/questions/45070117/r-check-if-special-character-in-string}
#'
#' \url{https://stackoverflow.com/questions/36928870/r-check-if-string-contains-special-characters}
#'
#' \url{https://stackoverflow.com/questions/14836754/is-there-an-r-function-to-escape-a-string-for-regex-characters{}}
#'
#' @param string The string
#' @param char A character used to delimit the string
#'
#' @importFrom stringr str_sub
#' @importFrom stringr str_locate
#'
#' @return A string
#' @export
#'
#' @examples
#' a <- c("left.right","left.right","left.right")
#' left(a, ".")
#' right(a, ".")
#'
#' library(dplyr)
#' library(tibble)
#'
#' test_df <- tibble::tibble(
#'   label = c("resection_margin=Mohs, > 1 cm",
#'             "resection_margin=Mohs, > 1 cm",
#'             "resection_margin=Mohs, <= 1 cm",
#'             "  resection_margin=Mohs, > 1 cm"))
#' test_df %>%
#'   mutate(left = left(label, "="),
#'          right = right(label, "="))
#'
#' right(test_df$label, "=")
#' left(test_df$label, "=")
#' stringr::str_trim(left(test_df$label, "="), side = "both")
#'

left <- function(string, char) {

  # From Hmisc::escapRegex
  char <- gsub("([.|()\\^{}+$*?]|\\[|\\])", "\\\\\\1", char)

  # stringr::str_sub(string,
  #                  start = 1,
  #                  end = stringr::str_locate(string,
  #                                            char)[, 1] - 1)

  stringr::str_split(string = string,
                     pattern = char,
                     n = 2,
                     simplify = TRUE)[, 1]


}


#' @rdname left
#' @export
right <- function(string, char) {

  # From Hmisc::escapRegex
  char <- gsub("([.|()\\^{}+$*?]|\\[|\\])", "\\\\\\1", char)

  # stringr::str_sub(string,
  #                  start = stringr::str_locate(string,
  #                                              char)[, 1] + 1,
  #                  end = nchar(string))

  stringr::str_split(string = string,
                     pattern = char,
                     n = 2,
                     simplify = TRUE)[, 2]

}





#### Old versions of these --------------------------------


#' #' @param string The string
#' #' @param char A character used to delimit the string
#' #' @param pattern Special characters that need to be escaped. Default is
#' #'   "/|:|\\?|<|>|\\|\\\\|\\*\\.()"
#' #'
#' #' @importFrom stringr str_sub
#' #' @importFrom stringr str_locate
#' #'
#' #' @return A string
#' #' @export
#' #'
#' #' @examples
#' #' a <- c("left.right","left.right","left.right")
#' #' left(a, ".")
#' #' right(a, ".")
#' #'
#' #' library(dplyr)
#' #' library(tibble)
#' #'
#' #' test_df <- tibble::tibble(
#' #'   label = c("resection_margin=Mohs, > 1 cm",
#' #'             "resection_margin=Mohs, > 1 cm",
#' #'             "resection_margin=Mohs, <= 1 cm",
#' #'             "  resection_margin=Mohs, > 1 cm"))
#' #' test_df %>%
#' #'   mutate(left = left(label, "="),
#' #'          right = right(label, "="))
#' #'
#' #' right(test_df$label, "=")
#' #' left(test_df$label, "=")
#' #' stringr::str_trim(left(test_df$label, "="), side = "both")
#' #'
#'
#' left <- function(string, char, pattern = "/|:|\\?|<|>|\\|\\\\|\\*\\.()") {
#'
#'   special <- pattern
#'
#'   if (grepl(char, special)) {
#'     esc <- "\\"
#'   } else {
#'     esc <- ""
#'   }
#'
#'   # substr(string,
#'   #        start = 1,
#'   #        stop = unlist(gregexpr(paste0(esc, char), string)) - 1)
#'
#'   stringr::str_sub(string,
#'                    start = 1,
#'                    end = stringr::str_locate(string,
#'                                                paste0(esc, char))[, 1] - 1)
#'
#' }
#'
#'
#' #' @rdname left
#' #' @export
#' right <- function(string, char, pattern = "/|:|\\?|<|>|\\|\\\\|\\*\\.()") {
#'
#'   special <- pattern
#'
#'   if (grepl(char, special)) {
#'     esc <- "\\"
#'   } else {
#'     esc <- ""
#'   }
#'
#'   # substr(string,
#'   #        start = unlist(gregexpr(paste0(esc, char), string)) + 1,
#'   #        stop = nchar(string))
#'
#'   stringr::str_sub(string,
#'                    start = stringr::str_locate(string,
#'                                                paste0(esc, char))[, 1] + 1,
#'                    end = nchar(string))
#'
#'
#' }
#'
#'
#'
#'
#'