Github user felixcheung commented on a diff in the pull request:
https://github.com/apache/spark/pull/20464#discussion_r172750404
--- Diff: docs/sparkr.md ---
@@ -663,3 +663,7 @@ You can inspect the search path in R with
[`search()`](https://stat.ethz.ch/R-ma
- The `stringsAsFactors` parameter was previously ignored with `collect`,
for example, in `collect(createDataFrame(iris), stringsAsFactors = TRUE))`. It
has been corrected.
- For `summary`, option for statistics to compute has been added. Its
output is changed from that from `describe`.
- A warning can be raised if versions of SparkR package and the Spark JVM
do not match.
+
+## Upgrading to Spark 2.4.0
+
+ - The `start` parameter of `substr` method was wrongly subtracted by one,
previously. In other words, the index specified by `start` parameter was
considered as 0-base. This can lead to inconsistent substring results and also
does not match with the behaviour with `substr` in R. It has been fixed so the
`start` parameter of `substr` method is now 1-base, e.g., `substr(df$a, 2, 5)`
should be changed to `substr(df$a, 1, 4)`.
--- End diff --
could you add
`method is now 1-base, e.g., therefore to get the same result as
substr(df$a, 2, 5), it should be changed to substr(df$a, 1, 4)`
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