as.character() function added to return vector of timestamps

NEWS.md

@@ -1,8 +1,13 @@
 # CFtime (development version)
 
-# CFtime 1.3.0
+Changes since release 1.3.0:
 
-Changes since release 1.2.0:
+* as.character() and length() methods added that return a vector of timestamps 
+or the number of offsets in a CFtime instance, respectively.
+* Minor code fixes, see GitHub commits.
+* Documentation updated, with description of new functions.
+
+# CFtime 1.3.0
 
 * Two CFtime instances can be added if they have compatible calendars and units.
 The earlier origin is preserved in the result and offsets from the later instance
@@ -20,8 +25,6 @@ timestamps is parsed and found to have different time zones, a warning is genera
 
 # CFtime 1.2.0
 
-Changes since release 1.1.0:
-
 * Datum units "years" and "months" added. While these units are discouraged by
 the CF Metadata Conventions due to their problematic definition, there are quite
 a few data sets out there that use these units nonetheless. For this reason,
@@ -46,8 +49,6 @@ previous behaviour so the API is not broken.
 
 # CFtime 1.1.0
 
-Changes since release 1.0.0:
-
 * CFtime() can now also be invoked with a vector of character timestamps as offsets, or
 with a single timestamp to create a complete time series from the datum to the
 indicated timestamp.

R/CFformat.R

@@ -37,14 +37,15 @@
 #' tail(CFtimestamp(cf2 + 1.5))
 CFtimestamp <- function(cf, format = NULL, asPOSIX = FALSE) {
   if (!(methods::is(cf, "CFtime"))) stop("First argument to CFtimestamp must be an instance of the `CFtime` class")
+  if (asPOSIX && calendar_id(cf@datum) != 1L) stop("Cannot make a POSIX timestamp on a non-standard calendar")
+
   time <- .offsets2time(cf@offsets, cf@datum)
   if (nrow(time) == 0L) return()
 
   if (is.null(format)) format <- ifelse(unit(cf@datum) < 4L || .has_time(time), "timestamp", "date")
   else if (!(format %in% c("date", "time", "timestamp"))) stop("Format specifier not recognized")
 
   if (asPOSIX) {
-    if (calendar_id(cf@datum) != 1L) stop("Cannot make a POSIX timestamp on a non-standard calendar")
     if (format == "date") ISOdate(time$year, time$month, time$day, 0L)
     else ISOdatetime(time$year, time$month, time$day, time$hour, time$minute, time$second, "UTC")
   } else {

R/CFtime.R

@@ -138,6 +138,21 @@ setMethod("length", "CFtime", function(x) {
   length(x@offsets)
 })
 
+#' Return the timestamps contained in the CFtime instance.
+#'
+#' @param x The CFtime instance whose timestamps will be returned
+#'
+#' @return The timestamps in the specified CFtime instance.
+#' @export
+#'
+#' @examples
+#' cf <- CFtime("days since 1850-01-01", "julian", 0:364)
+#' as.character(cf)
+setMethod("as.character", "CFtime", function(x) {
+  if (length(x@offsets) > 0)
+    CFtimestamp(x)
+})
+
 setMethod("show", "CFtime", function(object) {
   noff <- length(object@offsets)
   if (noff == 0L) {