R/units.R

In wikilake: Scrape Lake Metadata Tables from Wikipedia

# https://en.wikipedia.org/wiki/Template:Infobox_body_of_water

# specify default units
unit_key_ <- function(){
  unit_key <-
    "Variable, format, units\n
    Name, c, NA\n
    Location, c, NA\n
    Group, ?, NA\n
    Coordinates, ?, NA\n
    Type, ?, NA\n
    Etymology, ?, NA\n
    Part of, ?, NA\n
    Primary inflows, ?, NA\n
    River sources, ?, NA\n
    Primary outflows, ?, NA\n
    Ocean/sea sources, ?, NA\n
    Catchment area, n, km2\n
    Basin countries, ?, NA\n
    Managing agency, ?, NA\n
    Designation, ?, NA\n
    Built, ?, NA\n
    Construction engineer, ?, NA\n
    First flooded, ?, NA\n
    Max. length, n, km\n
    Max. width, n, km\n
    Surface area, n, km2\n
    Average depth, n, m\n
    Max. depth, n, m\n
    Water volume, n, m3\n
    Residence time, n, years\n
    Salinity, n, NA\n
    Shore length1, n, km\n
    Surface elevation, n, m\n
    Max. temperature, n, NA\n
    Min. temperature, n, NA\n
    Frozen, ?, NA\n
    Islands, ?, NA\n
    Sections/sub-basins, ?, NA\n
    Trenches, ?, NA\n
    Benches, ?, NA\n
    Settlements, ?, NA\n
    Website, ?, NA\n
    References, ?, NA"

  read.csv(textConnection(unit_key), stringsAsFactors = FALSE,
           strip.white = TRUE, sep = ",")
}

tidy_units <- function(res){
  unit_key <- unit_key_()

  known_units <- c("m", "km2", "years", "sq mi", "ha", "m3", "acres", "sq. km", "days", "acre feet")

  numeric_cols <- unit_key$Variable[unit_key$format == "n"]
  numeric_cols <- names(res) %in% numeric_cols
  numeric_cols <- names(res)[numeric_cols]

  if(length(numeric_cols) == 0){
    res
  }else{
    specified_cols    <- apply(res, 2,
                                function(x) any(
                                  stringr::str_detect(x, known_units)))
    specified_cols    <- names(res)[specified_cols]

    non_specified_cols <- numeric_cols[!(numeric_cols %in% specified_cols)]

    if(length(non_specified_cols) > 0){
       tryCatch({
         res[,non_specified_cols] <- unit_key[unit_key$Variable %in% non_specified_cols,]
      }, warning = function(w) {
        res
        })
    }

    # strip converted units
    # in case of a choice prefer default
    units_df <- data.frame(
      zero_units = sapply(res[,numeric_cols], function(x) pull_units(x, 0)),
      first_units = sapply(res[,numeric_cols], function(x) pull_units(x, 1)),
      second_units = sapply(res[,numeric_cols], function(x) pull_units(x, 2)))
    units_df$Variable <- row.names(units_df)

    units_df$use <- NA
    units_df <- merge(units_df, unit_key,
                      all.y = FALSE, all.x = TRUE, sort = FALSE)

    units_df$use <- lapply(seq_len(nrow(units_df)), function(x) {
        res <- which(units_df$units[x] ==
                     units_df[x, c("zero_units", "first_units", "second_units")]) - 1
        if(length(res) < 1){
          res <- 0
        }else{
          if(length(res) > 1){
            res <- res[1]
          }
        }
          res
        })

    res[,numeric_cols] <- sapply(seq_len(nrow(units_df)), function(x)
      pull_position(res[, numeric_cols[x]], units_df$use[x]))

    # assign units using the units package
    # res[,numeric_cols]
    quantities <- lapply(seq_len(length(numeric_cols)), function(x){

                          quantity <- res[,numeric_cols[x]]
                          quantity <- gsub(",", "", quantity)
                          quantity <- strsplit(quantity, " ")[[1]]

                          tryCatch(
                          units::set_units(as.numeric(quantity[1][1]),
                                           units::as_units(quantity[2]),
                                           mode = "standard"),
                          error = function(e){
                            trimws(paste(quantity, collapse = " "))
                            })
    })

    names(quantities) <- numeric_cols
    quantities        <- as.data.frame(quantities)
    names(quantities) <- numeric_cols

    res[,numeric_cols] <- quantities
  }

  res
}