Scottish postcode converter (function)

[Nic-Chr]

Proposing a function to convert postcodes to variables found in the Scottish postcode directory.

postcode_match <- function(x, group, factor = FALSE, ...){
  if (length(group) > 1) stop("Please supply a group of length 1")
  y <- gsub(" ", "", x, fixed = TRUE)
  y <- toupper(y)
  utils::data("spd_2021_1", envir = environment(), package = "phsmethods")
  postcodes <- spd_2021_1[["postcode"]]
  group_names <- spd_2021_1[[group]]
  y <- group_names[match(y, postcodes)]
  if (factor) {
    x_levels <- sort(unique(group_names))
    if (sum(is.na(y)) > 0) x_levels <- c(x_levels, NA_character_)
    y <- factor(y, levels = x_levels, ...)
  }
  return(y)
}

It could work like below:

> postcode_match("G2 1AL", group = "ca2019name")
[1] "Glasgow City"
> postcode_match("G2 1AL", group = "hb2019name")
[1] "Greater Glasgow and Clyde"
> postcode_match("G2 1AL", group = "date_of_introduction")
[1] "2011-05-03"
> postcode_match("G2 1AL", group = "hb2019name", factor = TRUE)
[1] Greater Glasgow and Clyde
14 Levels: Ayrshire and Arran Borders Dumfries and Galloway Fife Forth Valley Grampian Greater Glasgow and Clyde Highland Lanarkshire Lothian ... Western Isles