ianmcook commented on a change in pull request #1:
URL: https://github.com/apache/arrow-cookbook/pull/1#discussion_r674981383
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File path: r/content/manipulating_data.Rmd
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@@ -0,0 +1,66 @@
+# Manipulating Data
+
+## Computing Mean/Min/Max, etc value of an array
+
+Many base R functions such as `mean()`, `min()`, and `max()` have been mapped
to their Arrow equivalents, and so can be called on Arrow Array objects in the
same way. They will return Arrow object themselves.
+
+```{r, array_mean_na}
+my_values <- Array$create(c(1:5, NA))
+mean(my_values, na.rm = TRUE)
+```
+```{r, test_array_mean_na, opts.label = "test"}
+test_that("array_mean_na works as expected", {
+ expect_equal(mean(my_values, na.rm = TRUE), Scalar$create(3))
+})
+```
+If you want to use an R function which does not have an Arrow mapping, you can
use `as.vector()` to convert Arrow objects to base R vectors.
+
+```{r, fivenum}
+fivenum(as.vector(my_values))
+```
+```{r, test_fivenum, opts.label = "test"}
+test_that("fivenum works as expected", {
+ expect_equal(fivenum(as.vector(my_values)), 1:5)
+})
+```
+
+## Counting occurrences of elements in an array
+
+You can use `value_count()` to count elements in an Array.
Review comment:
I think a preamble like this is helpful, but maybe a bit pedantic:
```suggestion
Some functions in the Arrow R package do not have base R equivalents. In
other cases, the base R equivalents are not generic functions so they cannot be
called directly on Arrow Array objects.
For example, the `value_count()` function in the Arrow R package is loosely
equivalent to the base R function `table()`, which is not a generic function.
To count the elements in an R vector, you can use `table()`; to count the
elements in an Arrow Array, you can use `value_count()`.
```
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