R/strings.R

In surveydata: Tools to Work with Survey Data

###  String functions

#
#  surveydata/R/strings.R by Andrie de Vries  Copyright (C) 2011-2017
#
#  This program is free software; you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation; either version 2 or 3 of the License
#  (at your option).
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#
#  A copy of the GNU General Public License is available at
#  http://www.r-project.org/Licenses/
#


#' Finds the common and unique elements in a character vector.
#'
#' Function takes a character string as input and find the common and
#' unique elements.  Assumes that the common element is at start of string.
#'
#' @param string Character vector
#' @return list of common and unique strings
#' @keywords string
#' @export
#' @family Strings
#' @examples
#' test <- c("Q_1", "Q_2", "Q_3")
#' strCommonUnique(test)$common
#' strCommonUnique(test)$unique
strCommonUnique <- function(string) {
  x <- as.character(string)
  y <- string

  ## Handles case with a single string element
  if (length(x) <= 1) {
    return(list(common = x[1], unique = ""))
  }

  ## Handles case where all elements are identical
  all_identical <- all(as.logical(lapply(x, function(f) x[1] == f)))
  if (all_identical) {
    return(list(common = x[1], unique = rep("", length(x))))
  }

  ## Handles case where shortest element has length 0
  if (min(nchar(x)) == 0) {
    return(list(common = "", unique = x))
  }

  ## Handles case where shortest element has length 1
  if (min(nchar(x)) == 1) {
    x1 <- sapply(x, function(f) {
      unlist(strsplit(f, NULL))[1]
    })
    all_identical <- all(as.logical(lapply(x1, function(f) x1[1] == f)))
    if (all_identical) {
      return(
        list(common = substr(x[1], 1, 1), unique = substr(x, 2, nchar(x)))
      )
    } else {
      return(
        list(common = "", unique = x)
      )
    }
  }


  # Make all strings the same length as shortest string
  x1 <- substr(x, 1, min(nchar(x)))
  # Create matrix of characters
  split <- lapply(x1, function(f) {
    unlist(strsplit(f, NULL))
  })
  # Test which characters are identical
  identical <- sapply(split, function(f) {
    f == split[[1]]
  }) ### aaply
  common <- apply(identical, 2, function(f) {
    which(f == FALSE)[1]
  }) ### aaply
  mincommon <- min(common, na.rm = TRUE) - 1
  # browser()
  if (mincommon < 1) {
    return(list(common = "", unique = x))
  } else {
    return(list(
      common = substr(x[1], 1, mincommon),
      unique = substr(x, mincommon + 1, nchar(x))
    ))
  }
}