krlmlr commented on code in PR #285:
URL: https://github.com/apache/arrow-nanoarrow/pull/285#discussion_r1303297917
##########
r/R/convert-array.R:
##########
@@ -49,6 +49,12 @@
#' - [character()]: String and large string types can be converted to
#' [character()]. The conversion does not check for valid UTF-8: if you need
#' finer-grained control over encodings, use `to = blob::blob()`.
+#' - [factor()]: Dictionary-encoded arrays of strings can be converted to
+#' [factor()]; however, this must be specified explicitly (i.e.,
Review Comment:
Nit: do you need two links? It will be two links in the pkgdown docs anyway,
though.
```suggestion
#' `factor()`; however, this must be specified explicitly (i.e.,
```
##########
r/tests/testthat/test-convert-array.R:
##########
@@ -463,6 +501,77 @@ test_that("convert to vector works for null ->
character()", {
)
})
+test_that("convert to vector works for dictionary<string> -> character()", {
+ array <- as_nanoarrow_array(factor(letters[5:1]))
+
+ # Via S3 dispatch
+ expect_identical(
+ convert_array(array, character()),
+ c("e", "d", "c", "b", "a")
+ )
+
+ # Via C -> S3 dispatch
+ expect_identical(
+ convert_array.default(array, character()),
+ c("e", "d", "c", "b", "a")
+ )
+})
+
+test_that("convert to vector works for dictionary<string> -> factor()", {
+ array <- as_nanoarrow_array(factor(letters[5:1]))
+
+ # With empty levels
+ expect_identical(
+ convert_array(array, factor()),
+ factor(letters[5:1])
+ )
+
+ # With identical levels
+ expect_identical(
+ convert_array(array, factor(levels = c("a", "b", "c", "d", "e"))),
+ factor(letters[5:1])
+ )
+
+ # With mismatched levels
+ expect_identical(
+ convert_array(array, factor(levels = c("b", "a", "c", "e", "d"))),
+ factor(letters[5:1], levels = c("b", "a", "c", "e", "d"))
+ )
+
+ expect_error(
+ convert_array(array, factor(levels = c("f", "g", "h"))),
Review Comment:
Maybe:
```suggestion
convert_array(array, factor(levels = letters[-4])),
```
?
##########
r/R/convert-array.R:
##########
@@ -49,6 +49,12 @@
#' - [character()]: String and large string types can be converted to
#' [character()]. The conversion does not check for valid UTF-8: if you need
#' finer-grained control over encodings, use `to = blob::blob()`.
+#' - [factor()]: Dictionary-encoded arrays of strings can be converted to
+#' [factor()]; however, this must be specified explicitly (i.e.,
+#' `convert_array(array, factor())`) because arrays arriving
+#' in chunks can have dictionaries that contain different levels. Use
+#' `convert_array(array, factor(levels = c(...)))` to materialize an array
+#' into a vector with known levels.
#' - [Date][as.Date]: Only the date32 type can be converted to an R Date
vector.
Review Comment:
Unrelated:
```suggestion
#' - [Date][as.Date()]: Only the date32 type can be converted to an R Date
vector.
```
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