[DOCS] Clarify round mode for format_number & round functions

[roxannemoslehi]

What changes were proposed in this pull request?

Updated the description for the format_number description to indicate that it uses HALF_EVEN rounding. Updated the description for the round description to indicate that it uses HALF_UP rounding.

How was this patch tested?

Just changing the two function comments so no testing involved.

Please review http://spark.apache.org/contributing.html before opening a pull request.

[AmplabJenkins]

Can one of the admins verify this patch?

[srowen]

Have a look at http://spark.apache.org/contributing.html as the template says.
I think you'd want to describe this a little more, and consider whether other functions could use this detail?

[roxannemoslehi]

Hmm @srowen do you mean describe HALF_EVEN round mode? Also, I know some of the other functions that use this type of rounding already include it in their definition.

[srowen]

No I really meant fill out the PR a little more (see link). The title isn't descriptive.
If you mean this is just making the docs consistent that's great, just note that in the description here. Helps reviewers understand why you think this change should happen.

[ash211]

Thanks for contributing to Spark @roxannemoslehi !

I think Sean just means updating the title to something more like [DOCS] Clarify round mode in format_number function. It doesn't feel big enough to be worth a Jira ticket for such a small docs change.

[rxin]

Yea we definitely need a better title. Thanks for contributing though.

[rxin]

@roxannemoslehi can you fix the title? We can then merge this.

[roxannemoslehi]

Yup! Sorry about that everyone. Looks like my intended commit message didn't make it through originally but should be fixed now!

[srowen]

How about the doc of the round(Column) method earlier, same thing?

[roxannemoslehi]

Looks like round uses HALF_UP rounding mode

[rxin]

Thanks - merging in master.