jonkeane commented on a change in pull request #12433:
URL: https://github.com/apache/arrow/pull/12433#discussion_r817909766
##########
File path: r/R/dplyr-funcs-type.R
##########
@@ -76,6 +76,60 @@ register_bindings_type_cast <- function() {
register_binding("as.numeric", function(x) {
Expression$create("cast", x, options = cast_options(to_type = float64()))
})
+ register_binding("as.Date", function(x,
+ format = NULL,
+ tryFormats = "%Y-%m-%d",
+ origin = "1970-01-01",
+ tz = "UTC") {
+
+ if (call_binding("is.Date", x)) {
+ # base::as.Date() first converts to the desired timezone and then
extracts
+ # the date, which is why we need to go through timestamp() first
+ return(x)
+
+ # cast from POSIXct
+ } else if (call_binding("is.POSIXct", x)) {
+ if (tz == "UTC") {
+ x <- build_expr("cast", x, options = cast_options(to_type =
timestamp(timezone = tz)))
+ } else {
+ abort("`as.Date()` with a timezone different to 'UTC' is not supported
in Arrow")
+ }
+
+ # cast from character
+ } else if (call_binding("is.character", x)) {
+ # this could be improved with tryFormats once strptime returns NA and we
+ # can use coalesce - https://issues.apache.org/jira/browse/ARROW-15659
+ # TODO revisit once https://issues.apache.org/jira/browse/ARROW-15659 is
done
+ if (is.null(format)) {
+ if (length(tryFormats) == 1) {
+ format <- tryFormats[1]
+ } else {
+ abort("`as.Date()` with multiple `tryFormats` is not supported in
Arrow yet")
+ }
+ }
+ x <- build_expr("strptime", x, options = list(format = format, unit =
0L))
+
+ # cast from numeric
+ } else if (call_binding("is.numeric", x)) {
+ # the origin argument will be better supported once we implement temporal
+ # arithmetic (https://issues.apache.org/jira/browse/ARROW-14947)
+ # TODO revisit once the above has been sorted
+ if (!call_binding("is.integer", x)) {
+ # Arrow does not support direct casting from double to date so we have
+ # to convert to integers first - casting to int32() would error so we
+ # need to use `floor` before casting. `floor` is also a bit safer than
+ # int32() with `safe = FALSE` since it doesn't switch to `ceiling` for
+ # negative numbers
+ # TODO revisit if arrow decides to support double -> date casting
+ x <- call_binding("floor", x)
+ x <- build_expr("cast", x, options = cast_options(to_type = int32()))
+ }
+ if (origin != "1970-01-01") {
+ abort("`as.Date()` with an `origin` different than '1970-01-01' is not
supported in Arrow")
+ }
+ }
Review comment:
Like I mentioned above, I honestly hadn't caught that this was only
happening with numerics. We could put this at the top of the numeric if clause,
that would be fine (or we could have a two-condition if at the top to check
it). Though if someone _does_ provide an origin for anything other than
numerics we probably should error since that's not going to do anything for
them.
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