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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