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https://issues.apache.org/jira/browse/SPARK-31306?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Ben updated SPARK-31306:
------------------------
Description:
The rand() function in PySpark, Spark, and R is documented as drawing from
U[0.0, 1.0]. This suggests an inclusive upper bound, so can be confusing (i.e
for a distribution written as `X ~ U(a, b)`, x can be a or b, so `U[0.0, 1.0]`
suggests the value returned could include 1.0). The function uses Rand(), which
is documented as having a result in the range [0, 1). [documented here |
[https://github.com/apache/spark/blob/a1dbcd13a3eeaee50cc1a46e909f9478d6d55177/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/randomExpressions.scala#L71]]
was:`rand()` uses `Rand()` - which generates values in [0, 1) ([documented
here](https://github.com/apache/spark/blob/a1dbcd13a3eeaee50cc1a46e909f9478d6d55177/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/randomExpressions.scala#L71)).
The existing documentation suggests that 1.0 is a possible value returned by
rand (i.e for a distribution written as `X ~ U(a, b)`, x can be a or b, so
`U[0.0, 1.0]` suggests the value returned could include 1.0).
> rand() function documentation suggests an inclusive upper bound of 1.0
> ----------------------------------------------------------------------
>
> Key: SPARK-31306
> URL: https://issues.apache.org/jira/browse/SPARK-31306
> Project: Spark
> Issue Type: Documentation
> Components: PySpark, R, Spark Core
> Affects Versions: 2.4.5, 3.0.0
> Reporter: Ben
> Priority: Major
>
>
> The rand() function in PySpark, Spark, and R is documented as drawing from
> U[0.0, 1.0]. This suggests an inclusive upper bound, so can be confusing (i.e
> for a distribution written as `X ~ U(a, b)`, x can be a or b, so `U[0.0,
> 1.0]` suggests the value returned could include 1.0). The function uses
> Rand(), which is documented as having a result in the range [0, 1).
> [documented here |
> [https://github.com/apache/spark/blob/a1dbcd13a3eeaee50cc1a46e909f9478d6d55177/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/randomExpressions.scala#L71]]
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