## What changes were proposed in this pull request?

Add docs and examples for spark.ml.feature.Imputer. Currently scala and Java examples are included. Python example will be added after https://github.com/apache/spark/pull/17316

## How was this patch tested?

local doc generation and example execution

Author: Yuhao Yang <yuhao.yang@intel.com>

Closes #17324 from hhbyyh/imputerdoc.

## What changes were proposed in this pull request?
This PR is an enhancement to ML StringIndexer.
Before this PR, String Indexer only supports "skip"/"error" options to deal with unseen records.
But those unseen records might still be useful and user would like to keep the unseen labels in
certain use cases, This PR enables StringIndexer to support keeping unseen labels as
indices [numLabels].

'''Before
StringIndexer().setHandleInvalid("skip")
StringIndexer().setHandleInvalid("error")
'''After
support the third option "keep"
StringIndexer().setHandleInvalid("keep")

## How was this patch tested?
Test added in StringIndexerSuite

Signed-off-by: VinceShieh <vincent.xieintel.com>
(Please fill in changes proposed in this fix)

Author: VinceShieh <vincent.xie@intel.com>

Closes #16883 from VinceShieh/spark-17498.

## What changes were proposed in this pull request?
This pull request includes python API and examples for LSH. The API changes was based on yanboliang 's PR #15768 and resolved conflicts and API changes on the Scala API. The examples are consistent with Scala examples of MinHashLSH and BucketedRandomProjectionLSH.

## How was this patch tested?
API and examples are tested using spark-submit:
`bin/spark-submit examples/src/main/python/ml/min_hash_lsh.py`
`bin/spark-submit examples/src/main/python/ml/bucketed_random_projection_lsh.py`

User guide changes are generated and manually inspected:
`SKIP_API=1 jekyll build`

Author: Yun Ni <yunn@uber.com>
Author: Yanbo Liang <ybliang8@gmail.com>
Author: Yunni <Euler57721@gmail.com>

Closes #16715 from Yunni/spark-18080.

## What changes were proposed in this pull request?
Add FDR test case in ml/feature/ChiSqSelectorSuite.
Improve some comments in the code.
This is a follow-up pr for #15212.

## How was this patch tested?
ut

Author: Peng, Meng <peng.meng@intel.com>

Closes #16434 from mpjlu/fdr_fwe_update.

## What changes were proposed in this pull request?
There are many locations in the Spark repo where the same word occurs consecutively. Sometimes they are appropriately placed, but many times they are not. This PR removes the inappropriately duplicated words.

## How was this patch tested?
N/A since only docs or comments were updated.

Author: Niranjan Padmanabhan <niranjan.padmanabhan@gmail.com>

Closes #16455 from neurons/np.structure_streaming_doc.

[SPARK-17645][MLLIB][ML] add feature selector method based on: False Discovery Rate (FDR) and Family wise error rate (FWE)

## What changes were proposed in this pull request?

Univariate feature selection works by selecting the best features based on univariate statistical tests.
FDR and FWE are a popular univariate statistical test for feature selection.
In 2005, the Benjamini and Hochberg paper on FDR was identified as one of the 25 most-cited statistical papers. The FDR uses the Benjamini-Hochberg procedure in this PR. https://en.wikipedia.org/wiki/False_discovery_rate.
In statistics, FWE is the probability of making one or more false discoveries, or type I errors, among all the hypotheses when performing multiple hypotheses tests.
https://en.wikipedia.org/wiki/Family-wise_error_rate

We add  FDR and FWE methods for ChiSqSelector in this PR, like it is implemented in scikit-learn.
http://scikit-learn.org/stable/modules/feature_selection.html#univariate-feature-selection
## How was this patch tested?

ut will be added soon

(Please explain how this patch was tested. E.g. unit tests, integration tests, manual tests)

(If this patch involves UI changes, please attach a screenshot; otherwise, remove this)

Author: Peng <peng.meng@intel.com>
Author: Peng, Meng <peng.meng@intel.com>

Closes #15212 from mpjlu/fdr_fwe.

## What changes were proposed in this pull request?
The user guide for LSH is added to ml-features.md, with several scala/java examples in spark-examples.

## How was this patch tested?
Doc has been generated through Jekyll, and checked through manual inspection.

Author: Yunni <Euler57721@gmail.com>
Author: Yun Ni <yunn@uber.com>
Author: Joseph K. Bradley <joseph@databricks.com>
Author: Yun Ni <Euler57721@gmail.com>

Closes #15795 from Yunni/SPARK-18081-lsh-guide.

## What changes were proposed in this pull request?
API review for 2.1, except ```LSH``` related classes which are still under development.

## How was this patch tested?
Only doc changes, no new tests.

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #16009 from yanboliang/spark-18318.

## What changes were proposed in this pull request?
1, There are two `[Graph.partitionBy]` in `graphx-programming-guide.md`, the first one had no effert.
2, `DataFrame`, `Transformer`, `Pipeline` and `Parameter`  in `ml-pipeline.md` were linked to `ml-guide.html` by mistake.
3, `PythonMLLibAPI` in `mllib-linear-methods.md` was not accessable, because class `PythonMLLibAPI` is private.
4, Other link updates.
## How was this patch tested?
 manual tests

Author: Zheng RuiFeng <ruifengz@foxmail.com>

Closes #15912 from zhengruifeng/md_fix.

## What changes were proposed in this pull request?
1, `**Example**` => `**Examples**`, because more algos use `**Examples**`.
2,  delete `### Examples` in `Isotonic regression`, because it's not that special in http://spark.apache.org/docs/latest/ml-classification-regression.html
3, add missing marks for `LDA` and other algos.

## How was this patch tested?
No tests for it only modify doc

Author: Zheng RuiFeng <ruifengz@foxmail.com>

Closes #15783 from zhengruifeng/doc_fix.

I created Scala and Java example and added documentation.

Author: chie8842 <hayashidac@nttdata.co.jp>

Closes #15658 from hayashidac/SPARK-13770.

## What changes were proposed in this pull request?
- Renamed kbest to numTopFeatures
- Renamed alpha to fpr
- Added missing Since annotations
- Doc cleanups
## How was this patch tested?

Added new standardized unit tests for spark.ml.
Improved existing unit test coverage a bit.

Author: Joseph K. Bradley <joseph@databricks.com>

Closes #15647 from jkbradley/chisqselector-follow-ups.

## What changes were proposed in this pull request?

This PR is an enhancement of PR with commit ID:57dc326b.
NaN is a special type of value which is commonly seen as invalid. But We find that there are certain cases where NaN are also valuable, thus need special handling. We provided user when dealing NaN values with 3 options, to either reserve an extra bucket for NaN values, or remove the NaN values, or report an error, by setting handleNaN "keep", "skip", or "error"(default) respectively.

'''Before:
val bucketizer: Bucketizer = new Bucketizer()
          .setInputCol("feature")
          .setOutputCol("result")
          .setSplits(splits)
'''After:
val bucketizer: Bucketizer = new Bucketizer()
          .setInputCol("feature")
          .setOutputCol("result")
          .setSplits(splits)
          .setHandleNaN("keep")

## How was this patch tested?
Tests added in QuantileDiscretizerSuite, BucketizerSuite and DataFrameStatSuite

Signed-off-by: VinceShieh <vincent.xieintel.com>

Author: VinceShieh <vincent.xie@intel.com>
Author: Vincent Xie <vincent.xie@intel.com>
Author: Joseph K. Bradley <joseph@databricks.com>

Closes #15428 from VinceShieh/spark-17219_followup.

## What changes were proposed in this pull request?

A follow up for #14597 to update feature selection docs about ChiSqSelector.

## How was this patch tested?

Generated html docs. It can be previewed at:

* ml: http://sparkdocs.lins05.pw/spark-17017/ml-features.html#chisqselector
* mllib: http://sparkdocs.lins05.pw/spark-17017/mllib-feature-extraction.html#chisqselector

Author: Shuai Lin <linshuai2012@gmail.com>

Closes #15236 from lins05/spark-17017-update-docs-for-chisq-selector-fpr.

## What changes were proposed in this pull request?
This PR fixes an issue when Bucketizer is called to handle a dataset containing NaN value.
Sometimes, null value might also be useful to users, so in these cases, Bucketizer should
reserve one extra bucket for NaN values, instead of throwing an illegal exception.
Before:
```
Bucketizer.transform on NaN value threw an illegal exception.
```
After:
```
NaN values will be grouped in an extra bucket.
```
## How was this patch tested?
New test cases added in `BucketizerSuite`.
Signed-off-by: VinceShieh <vincent.xieintel.com>

Author: VinceShieh <vincent.xie@intel.com>

Closes #14858 from VinceShieh/spark-17219.

## What changes were proposed in this pull request?

Allow centering / mean scaling of sparse vectors in StandardScaler, if requested. This is for compatibility with `VectorAssembler` in common usages.

## How was this patch tested?

Jenkins tests, including new caes to reflect the new behavior.

Author: Sean Owen <sowen@cloudera.com>

Closes #14663 from srowen/SPARK-17001.

## What changes were proposed in this pull request?
The ```ml.feature.Normalizer``` examples illustrate L1 norm rather than L2, we should correct corresponding document.
![image](https://cloud.githubusercontent.com/assets/1962026/17928637/85aec284-69b0-11e6-9b13-d465ee560581.png)

## How was this patch tested?
Doc change, no test.

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #14787 from yanboliang/normalizer.

## What changes were proposed in this pull request?

Fixed several inline formatting in ml features doc.

Before:

<img width="475" alt="screen shot 2016-07-14 at 12 24 57 pm" src="https://cloud.githubusercontent.com/assets/717363/16827974/1e1b6e04-49be-11e6-8aa9-4a0cb6cd3b4e.png">

After:

<img width="404" alt="screen shot 2016-07-14 at 12 25 48 pm" src="https://cloud.githubusercontent.com/assets/717363/16827976/2576510a-49be-11e6-96dd-92a1fa464d36.png">

## How was this patch tested?

Genetate the docs locally by `SKIP_API=1 jekyll build` and view it in the browser.

Author: Shuai Lin <linshuai2012@gmail.com>

Closes #14194 from lins05/fix-docs-formatting.

## What changes were proposed in this pull request?

Made DataFrame-based API primary
* Spark doc menu bar and other places now link to ml-guide.html, not mllib-guide.html
* mllib-guide.html keeps RDD-specific list of features, with a link at the top redirecting people to ml-guide.html
* ml-guide.html includes a "maintenance mode" announcement about the RDD-based API
  * **Reviewers: please check this carefully**
* (minor) Titles for DF API no longer include "- spark.ml" suffix.  Titles for RDD API have "- RDD-based API" suffix
* Moved migration guide to ml-guide from mllib-guide
  * Also moved past guides from mllib-migration-guides to ml-migration-guides, with a redirect link on mllib-migration-guides
  * **Reviewers**: I did not change any of the content of the migration guides.

Reorganized DataFrame-based guide:
* ml-guide.html mimics the old mllib-guide.html page in terms of content: overview, migration guide, etc.
* Moved Pipeline description into ml-pipeline.html and moved tuning into ml-tuning.html
  * **Reviewers**: I did not change the content of these guides, except some intro text.
* Sidebar remains the same, but with pipeline and tuning sections added

Other:
* ml-classification-regression.html: Moved text about linear methods to new section in page

## How was this patch tested?

Generated docs locally

Author: Joseph K. Bradley <joseph@databricks.com>

Closes #14213 from jkbradley/ml-guide-2.0.

## What changes were proposed in this pull request?

Made changes to HashingTF,QuantileVectorizer and CountVectorizer

Author: GayathriMurali <gayathri.m@intel.com>

Closes #13745 from GayathriMurali/SPARK-15997.

## What changes were proposed in this pull request?

jira: https://issues.apache.org/jira/browse/SPARK-16045
2.0 Audit: Update document for StopWordsRemover and Binarizer.

## How was this patch tested?

manual review for doc

Author: Yuhao Yang <hhbyyh@gmail.com>
Author: Yuhao Yang <yuhao.yang@intel.com>

Closes #13375 from hhbyyh/stopdoc.

## What changes were proposed in this pull request?

Correct some typos and incorrectly worded sentences.

## How was this patch tested?

Doc changes only.

Note that many of these changes were identified by whomfire01

Author: sethah <seth.hendrickson16@gmail.com>

Closes #13180 from sethah/ml_guide_audit.

## What changes were proposed in this pull request?

We should now begin copying algorithm details from the spark.mllib guide to spark.ml as needed, rather than just linking back to the corresponding algorithms in the spark.mllib user guide.

## How was this patch tested?

manual review for doc.

Author: Yuhao Yang <hhbyyh@gmail.com>
Author: Yuhao Yang <yuhao.yang@intel.com>

Closes #12957 from hhbyyh/tfidfdoc.

## What changes were proposed in this pull request?
Fixed some minor errors found when reviewing feature.ml user guide

## How was this patch tested?
built docs locally

Author: Bryan Cutler <cutlerb@gmail.com>

Closes #12940 from BryanCutler/feature.ml-doc_fixes-DOCS-MINOR.

## What changes were proposed in this pull request?
Add the missing python example for QuantileDiscretizer

## How was this patch tested?
manual tests

Author: Zheng RuiFeng <ruifengz@foxmail.com>

Closes #12281 from zhengruifeng/discret_pe.

## What changes were proposed in this pull request?
Add the missing python example for VectorSlicer

## How was this patch tested?
manual tests

Author: Zheng RuiFeng <ruifengz@foxmail.com>

Closes #12282 from zhengruifeng/vecslicer_pe.

## What changes were proposed in this pull request?

Currently, the docs for TF-IDF only refer to using HashingTF with IDF. However, CountVectorizer can also be used. We should probably amend the user guide and examples to show this.

## How was this patch tested?

unit tests and doc generation

Author: Yuhao Yang <hhbyyh@gmail.com>

Closes #12454 from hhbyyh/tfdoc.

## What changes were proposed in this pull request?
Add the missing python example for ChiSqSelector

## How was this patch tested?
manual tests

Author: Zheng RuiFeng <ruifengz@foxmail.com>

Closes #12283 from zhengruifeng/chi2_pe.

## What changes were proposed in this pull request?
Add python CountVectorizerExample

## How was this patch tested?
manual tests

Author: Zheng RuiFeng <ruifengz@foxmail.com>

Closes #11917 from zhengruifeng/cv_pe.

## What changes were proposed in this pull request?
add three python examples

## How was this patch tested?
manual tests

Author: Zheng RuiFeng <ruifengz@foxmail.com>

Closes #12063 from zhengruifeng/dct_pe.

## What changes were proposed in this pull request?

jira: https://issues.apache.org/jira/browse/SPARK-13512
Add example and doc for ml.feature.MaxAbsScaler.

## How was this patch tested?
 unit tests

Author: Yuhao Yang <hhbyyh@gmail.com>

Closes #11392 from hhbyyh/maxabsdoc.

## What changes were proposed in this pull request?

This PR tries to fix all typos in all markdown files under `docs` module,
and fixes similar typos in other comments, too.

## How was the this patch tested?

manual tests.

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #11300 from dongjoon-hyun/minor_fix_typos.

Update user guide for RFormula feature interactions. Meanwhile we also update other new features such as supporting string label in Spark 1.6.

Author: Yanbo Liang <ybliang8@gmail.com>

Closes #10222 from yanboliang/spark-11965.

Follow-up of [SPARK-12199](https://issues.apache.org/jira/browse/SPARK-12199) and #10193 where a broken link has been left as is.

Author: BenFradet <benjamin.fradet@gmail.com>

Closes #10282 from BenFradet/SPARK-12199.

https://issues.apache.org/jira/browse/SPARK-12199

Follow-up PR of SPARK-11551. Fix some errors in ml-features.md

mengxr

Author: Xusen Yin <yinxusen@gmail.com>

Closes #10193 from yinxusen/SPARK-12199.

Added a paragraph regarding StringIndexer#setHandleInvalid to the ml-features documentation.

I wonder if I should also add a snippet to the code example, input welcome.

Author: BenFradet <benjamin.fradet@gmail.com>

Closes #10257 from BenFradet/SPARK-12217.

[SPARK-12212][ML][DOC] Clarifies the difference between spark.ml, spark.mllib and mllib in the documentation.

Replaces a number of occurences of `MLlib` in the documentation that were meant to refer to the `spark.mllib` package instead. It should clarify for new users the difference between `spark.mllib` (the package) and MLlib (the umbrella project for ML in spark).

It also removes some files that I forgot to delete with #10207

Author: Timothy Hunter <timhunter@databricks.com>

Closes #10234 from thunterdb/12212.

PR on behalf of somideshmukh, thanks!

Author: Xusen Yin <yinxusen@gmail.com>
Author: somideshmukh <somilde@us.ibm.com>

Closes #10219 from yinxusen/SPARK-11551.

This PR moves pieces of the spark.ml user guide to reflect suggestions in SPARK-8517. It does not introduce new content, as requested.

<img width="192" alt="screen shot 2015-12-08 at 11 36 00 am" src="https://cloud.githubusercontent.com/assets/7594753/11666166/e82b84f2-9d9f-11e5-8904-e215424d8444.png">

Author: Timothy Hunter <timhunter@databricks.com>

Closes #10207 from thunterdb/spark-8517.

Documentation regarding the `IndexToString` label transformer with code snippets in Scala/Java/Python.

Author: BenFradet <benjamin.fradet@gmail.com>

Closes #10166 from BenFradet/SPARK-12159.