Datetime fxns

NAMESPACE

@@ -3,8 +3,10 @@
 export(DC_col_check)
 export(check_dc_cols)
 export(check_te)
+export(convert_datetime_format)
 export(convert_long_to_utm)
 export(convert_utm_to_ll)
+export(fix_utc_offset)
 export(create_datastore_script)
 export(fuzz_location)
 export(get_custom_flags)

QCkit.Rproj

@@ -17,3 +17,4 @@ StripTrailingWhitespace: Yes
 BuildType: Package
 PackageUseDevtools: Yes
 PackageInstallArgs: --no-multiarch --with-keep.source
+PackageRoxygenize: rd,collate,namespace

R/dates_and_times.R

@@ -0,0 +1,76 @@
+#' Fix UTC offset strings
+#' 
+#' UTC offsets can be formatted in multiple ways (e.g. -07, -07:00, -0700) and R often struggles to parse these offsets. This function takes date/time strings with valid UTC offsets, and formats them so that they are consistent and readable by R.
+#'
+#' @param datetime_strings Character vector of dates in ISO 8601 format
+#'
+#' @return datetime_strings with UTC offsets consistently formatted to four digits (e.g. "2023-11-16T03:32:49-0700").
+#' @export
+#'
+#' @examples
+#' datetimes <- c("2023-11-16T03:32:49+07:00","2023-11-16T03:32:49-07","2023-11-16T03:32:49","2023-11-16T03:32:49Z")
+#' fix_utc_offset(datetimes)  # returns c("2023-11-16T03:32:49+0700", "2023-11-16T03:32:49-0700", "2023-11-16T03:32:49", "2023-11-16T03:32:49+0000") and warns about missing offset (see third element)
+#' 
+fix_utc_offset <- function(datetime_strings) {
+  datetime_strings <- stringr::str_replace_all(datetime_strings, "[−‐‑‒–—―﹘﹣－]", "-") # replace every possible type of dash with a regular minus sign
+
+  # get UTC offset and format it as 4 digits with no special characters (e.g. 0700)
+  new_offsets <- datetime_strings %>%
+    stringr::str_extract("[Zz]|((?<=[+-])[0-9]{1,2}:?[0-9]{0,2})$") %>%
+    stringr::str_remove(":") %>%
+    stringr::str_replace("[Zz]", "0000")
+  new_offsets <- dplyr::case_when(nchar(new_offsets) == 1 ~ paste0("0", new_offsets, "00"),
+                                  nchar(new_offsets) == 2 ~ paste0(new_offsets, "00"),
+                                  nchar(new_offsets) == 4 ~ new_offsets,
+                                  .default = "")
+  if (any(new_offsets == "")) {
+    warning("Date strings contain missing or invalid UTC offsets")
+  }
+
+  # remove old UTC offsets from date strings
+  datetime_strings <- datetime_strings %>%
+    stringr::str_remove("(?<=[+-])[0-9]{1,2}:?[0-9]{0,2}$") %>%
+    stringr::str_replace("[Zz](?=$)", "+")
+
+  # add new UTC offsets
+  datetime_strings <- paste0(datetime_strings, new_offsets) %>%
+    stringr::str_remove("[+-](?=$)")  # Remove trailing + or - where invalid offsets were removed
+
+  return(datetime_strings)
+}
+
+#' Convert EML date/time format string to one that R can parse
+#'
+#' @details `convert_datetime_format()` is not a sophisticated function. If the EML format string is not valid, it will happily and without complaint return an R format string that will break your code. You have been warned.  Note that UTC offset formats using a colon or only two digits will be parsed by this function, but if parsing datetime values from strings, you will also need to use `fix_utc_offset` to change the UTC offsets to the +/-hhhh format that R can read.
+#'
+#' @param eml_format_string A character vector of EML date/time format strings. This function understands the following codes: YYYY = four digit year, YY = two digit year, MMM = three letter month abbrev., MM = two digit month, DD = two digit day, hh or HH = 24 hour time, mm = minutes, ss or SS = seconds, +/-hhhh or +/-HHHH = UTC offset.
+#' @param convert_z Should a "Z" at the end of the format string (indicating UTC) be replaced by a "%z"? Only set to `TRUE` if you plan to use `fix_utc_offset` to change "Z" in datetime strings to "+0000". 
+#'
+#' @return A character vector of date/time format strings that can be parsed by `readr` or `strptime`.
+#' @export
+#'
+#' @examples
+#' convert_datetime_format("MM/DD/YYYY")
+#' convert_datetime_format(c("MM/DD/YYYY", "YY-MM-DD"))
+#'
+convert_datetime_format <- function(eml_format_string, convert_z = FALSE) {
+  r_format_string <- eml_format_string %>%
+    stringr::str_replace_all("YYYY", "%Y") %>%
+    stringr::str_replace_all("YY", "%y") %>%
+    stringr::str_replace_all("MMM", "%b") %>%
+    stringr::str_replace_all("MM", "%m") %>%
+    stringr::str_replace_all("DD", "%d") %>%
+    stringr::str_replace_all("(?<![+-])((hh)|(HH))", "%H") %>%
+    stringr::str_replace_all("mm", "%M") %>%
+    stringr::str_replace_all("(ss)|(SS)", "%S") %>%
+    stringr::str_replace_all("(?<!%)M", "%m") %>%  # Replace M with %m, but leave %M alone
+    stringr::str_replace_all("D", "%d") %>%
+    stringr::str_replace_all("[+-][Hh]{1,2}:?[Hh]{0,2}(?=$)", "%z")  # Replace UTC offset format string (e.g. -hh, -hhhh, -hh:hh) with %z. Note that R seems to only parse UTC offsets when in the format +/-hhhh.
+  #stringr::str_replace_all("T", " ")
+
+  if (convert_z) {
+    r_format_string <- stringr::str_replace(r_format_string, "Z(?=$)", "%z")
+  }
+
+  return(r_format_string)
+}