R/sanitizeTexString.R

In tikzDevice: R Graphics Output in LaTeX Format

#' Replace LaTeX Special Characters in a String
#'
#' This function is used by tikzDevice when `sanitize = TRUE` to replace
#' special LaTeX characters (such as the comment character %) in plotting text
#' where the user does not have direct control over the generated text.
#'
#' `sanitizeTexString()` searches character by character through a string
#' replacing each occurrence of a special character contained in
#' `strip[i]` with the corresponding replacement value in
#' `replacement[i]`.  tikzDevice calls back this function for every piece
#' of text when the sanitize option is TRUE. See [tikz()] for more
#' information on the default special characters and replacement values.
#'
#' By default, `tikzSanitizeCharacters` replaces the following characters:
#'
#' \itemize{
#'   \item \verb{\%}
#'   \item \verb{$}
#'   \item \verb{\}}
#'   \item \verb{\{}
#'   \item \verb{^}
#'   \item \verb{_}
#'   \item \verb{#}
#'   \item \verb{&}
#'   \item \verb{~}
#' }
#'
#' With the contents of `tikzReplacementCharacters`:
#'
#' \itemize{
#'   \item \verb{\\\%}
#'   \item \verb{\\$}
#'   \item \verb{\\\}}
#'   \item \verb{\\\{}
#'   \item \verb{\\^{}}
#'   \item \verb{\\_{}}
#'   \item \verb{\\#}
#'   \item \verb{\\&}
#'   \item \verb{\char`\~}
#'  }
#'
#' These defaults may be adjusted using the [options()] function.
#'
#' @param string A character vector of length 1 (a string).
#' @param strip A character vector of single characters to search for.
#' @param replacement A character vector of replacement values.
#'
#' @return \item{sanitizedString}{A character vector of length 1 with all
#'   special characters replaced.}
#'
#' @author Cameron Bracken \email{cameron.bracken@@gmail.com}
#'
#' @seealso [tikz()]
#' @keywords character
#'
#' @examples
#'
#' # Be careful with sanitizing, it may lead to unexpected behavior.
#' # For example, we may want -1 to be a superscript it gets
#' # sanitized away with the other default special characters.
#' # The string appears in LaTeX exactly as shown.
#' \dontrun{
#'   sanitizeTexString('10\% of 10$ is 10^\{-1\}$')
#' }
#'
#' @export
sanitizeTexString <- function(string,
                              strip = getOption("tikzSanitizeCharacters"),
                              replacement = getOption("tikzReplacementCharacters")) {

  # separate the string into a vector of charaters
  explode <- strsplit(string, "")[[1]]
  if (any(is.na(explode))) stop("Unable to sanitize string, you may be trying to pass in an unsupported symbol")

  # Replace each matching character with its replacement characters
  for (i in 1:length(explode)) {
    matches <- (explode[i] == strip)
    if (any(matches)) {
      explode[i] <- paste("{", replacement[which(matches)], "}", sep = "")
    }
  }
  # stick the string back together
  return(paste(explode, collapse = ""))
}