[SPARK-16109][SPARKR][DOC] R more doc fixes

[felixcheung]

What changes were proposed in this pull request?

Found these issues while reviewing for SPARK-16090

How was this patch tested?

roxygen2 doc gen, checked output html

[felixcheung]

@shivaram

[SparkQA]

Test build #60920 has finished for PR 13803 at commit 9ff4e6e.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #60924 has finished for PR 13803 at commit 1d6e9c5.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[shivaram]

cc @mengxr

[shivaram]

@felixcheung Can you change the JIRA in the title to https://issues.apache.org/jira/browse/SPARK-16109 ? I created a sub-task for statfunctions

[shivaram]

can we have a @family stat_functions here to point users to other stat functions ?

[shivaram]

Other than the comment about the family link the rest of the changes look good

[felixcheung]

done - @family doesn't need to be one word so added "stat functions"

[shivaram]

Thanks - rebuilt locally and the docs look good. Will merge after Jenkins passes

[SparkQA]

Test build #60942 has finished for PR 13803 at commit 0bc74c3.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[shivaram]

LGTM. Merging this

[felixcheung]

Great! Thanks! Hopefully now docs are in much better shape.

[shivaram]

Yeah - thanks for all the work in cleaning this up. One thing that i was wondering is we could add some style guide checks or contribution guide rules on how to maintain documentation. We can discuss this in SPARK-16090 or in a new JIRA

[felixcheung]

I have been thinking about the same thing - problem is people generally do not read contribution guide :) if there is a way to get automatic style check it would be good.

[shivaram]

Irrespective of people reading the guide, it'll at least be useful to point out what is the expected documentation layout in a code review etc. But yeah automatic style checks would be really cool.