convert character dms to decimal degrees

dms2dec.R

# Good discussion on str_extract/str_match and positive look behind
# https://stackoverflow.com/questions/35804379/stringr-str-extract-how-to-do-positive-lookbehind
dms2dec <- function(string) {
  string <- 
    str_squish(string) %>% 
    str_replace_all(., "\\s", "")

  values <- str_match(string, "(\\d*)[\\u00B0|˚]\\s?(\\d*\\.?\\d*?)('|′|’)\\s?(\\d*?\\.?\\d*?)[\"|″]?\\s?(N|n|E|e|S|s|W|w)")

  original <- values[, 1]
  degrees <- values[, 2]
  minutes <- (values[, 3])
  seconds <- values[, 5]
  direction <- values[, 6]

  degrees <- as.numeric(degrees)
  minutes <- ifelse(!is.na(as.numeric(minutes)), as.numeric(minutes), 0)
  seconds <- ifelse(!is.na(as.numeric(seconds)), as.numeric(seconds), 0)

  dms <- degrees + minutes / 60 + seconds / 3600

  dms <- ifelse(direction %in% c("N", "n", "E", "e"), 1 * dms, -1 * dms)

  return(dms)
}

Still need to have some clean up and should probably use str_squish to simplify regex.

str_squish didn't do what I thought it did, but I kept it anyway, needed to add str_replace_all to get rid of all whitespace so I could stop worrying about it

Also had to update separators