[SPARK-11689] [ML] Add user guide and example code for LDA under spark.ml

[hhbyyh]

jira: https://issues.apache.org/jira/browse/SPARK-11689

Add simple user guide for LDA under spark.ml and example code under examples/. Use include_example to include example code in the user guide markdown. Check SPARK-11606 for instructions.

[SparkQA]

Test build #45951 has finished for PR 9722 at commit 8a6d2d6.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):\n * public class JavaLDAExample\n

[SparkQA]

Test build #46061 has finished for PR 9722 at commit 195c85c.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):\n * public class JavaLDAExample\n

[mengxr]

cc: @feynmanliang

[feynmanliang]

The other links in this section are sorted alphabetically

[feynmanliang]

Made a pass

[SparkQA]

Test build #46336 has finished for PR 9722 at commit 5e22624.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):\n * public class JavaLDAExample\n

[feynmanliang]

I thought this was supposed to read "In this section, we introduce the pipeline API for clustering in mllib"? The pipelines API doesn't "correspond" to mllib since it's missing a lot of features

[feynmanliang]

LGTM after changes

[hhbyyh]

ERROR: Timeout after 15 minutes
ERROR: Error fetching remote repo 'origin'
hudson.plugins.git.GitException: Failed to fetch from https://github.com/apache/spark.git

[feynmanliang]

LGTM

[feynmanliang]

Jenkins test this please

[SparkQA]

Test build #46408 has finished for PR 9722 at commit c794096.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):\n * public class JavaLDAExample\n

[mengxr]

Merged into master and branch-1.6. Thanks!

[mengxr]

@hhbyyh I reverted the commit because it failed doc build. Could you re-open this PR and try SKIP_API=1 jekyll build on your local. I thought this is tested in PR build but actually not. Sorry!

[hhbyyh]

I'll look into it immediately. Sorry for the troubling.
This takes longer than I thought, as I'm still struggling to config my local environment for document build via all kinds of proxies, thanks to Chinese network....

[yinxusen]

@hhbyyh The Java example is lack of // $example on$ and // $example off$.

[yinxusen]

@mengxr It's really a problem of testing example code and markdown doc in the test time. I think Spark QA cannot grasp this kind of errors.

[hhbyyh]

@yinxusen Thanks a lot. It seems I cannot reopen the PR. I'll create a new one.

Yet I keep getting error compiling QueryExecutionListener.scala during build/sbt unidoc. Have you met a similar issue?

[yinxusen]

@hhbyyh I am not familiar with sbt unidoc, but since it is an example file, there is no need to generate API docs and check them. You can use SKIP_API=1 jekyll serve --watch to avoid generating API docs.

[hhbyyh]

Yes Thanks.