[[SPARK-9249] local variable assigned but may not be used - ASF JIRA](https://issues.apache.org/jira/browse/SPARK-9249)

https://gist.github.com/yu-iskw/0e5b0253c11769457ea5

Author: Yu ISHIKAWA <yuu.ishikawa@gmail.com>

Closes #7640 from yu-iskw/SPARK-9249 and squashes the following commits:

7a51cab [Yu ISHIKAWA] [SPARK-9249][SparkR] local variable assigned but may not be used

We forgot to update doc. brkyvz

Author: Xiangrui Meng <meng@databricks.com>

Closes #7608 from mengxr/SPARK-9243 and squashes the following commits:

0ea3236 [Xiangrui Meng] null -> zero in crosstab doc

Add `crosstab` to SparkR DataFrames, which takes two column names and returns a local R data.frame. This is similar to `table` in R. However, `table` in SparkR is used for loading SQL tables as DataFrames. The return type is data.frame instead table for `crosstab` to be compatible with Scala/Python.

I couldn't run R tests successfully on my local. Many unit tests failed. So let's try Jenkins.

Author: Xiangrui Meng <meng@databricks.com>

Closes #7318 from mengxr/SPARK-8364 and squashes the following commits:

d75e894 [Xiangrui Meng] fix tests
53f6ddd [Xiangrui Meng] fix tests
f1348d6 [Xiangrui Meng] update test
47cb088 [Xiangrui Meng] Merge remote-tracking branch 'apache/master' into SPARK-8364
5621262 [Xiangrui Meng] first version without test

This exposes the SparkR:::glm() and SparkR:::predict() APIs. It was necessary to change RFormula to silently drop the label column if it was missing from the input dataset, which is kind of a hack but necessary to integrate with the Pipeline API.

The umbrella design doc for MLlib + SparkR integration can be viewed here: https://docs.google.com/document/d/10NZNSEurN2EdWM31uFYsgayIPfCFHiuIu3pCWrUmP_c/edit

mengxr

Author: Eric Liang <ekl@databricks.com>

Closes #7483 from ericl/spark-8774 and squashes the following commits:

3dfac0c [Eric Liang] update
17ef516 [Eric Liang] more comments
1753a0f [Eric Liang] make glm generic
b0f50f8 [Eric Liang] equivalence test
550d56d [Eric Liang] export methods
c015697 [Eric Liang] second pass
117949a [Eric Liang] comments
5afbc67 [Eric Liang] test label columns
6b7f15f [Eric Liang] Fri Jul 17 14:20:22 PDT 2015
3a63ae5 [Eric Liang] Fri Jul 17 13:41:52 PDT 2015
ce61367 [Eric Liang] Fri Jul 17 13:41:17 PDT 2015
0299c59 [Eric Liang] Fri Jul 17 13:40:32 PDT 2015
e37603f [Eric Liang] Fri Jul 17 12:15:03 PDT 2015
d417d0c [Eric Liang] Merge remote-tracking branch 'upstream/master' into spark-8774
29a2ce7 [Eric Liang] Merge branch 'spark-8774-1' into spark-8774
d1959d2 [Eric Liang] clarify comment
2db68aa [Eric Liang] second round of comments
dc3c943 [Eric Liang] address comments
5765ec6 [Eric Liang] fix style checks
1f361b0 [Eric Liang] doc
d33211b [Eric Liang] r support
fb0826b [Eric Liang] [SPARK-8774] Add R model formula with basic support as a transformer

[[SPARK-9052] Fix comments after curly braces - ASF JIRA](https://issues.apache.org/jira/browse/SPARK-9052)

This is the full result of lintr at the rivision:01155162.
[[SPARK-9052] the result of lint-r at the revision:01155162](https://gist.github.com/yu-iskw/e7246041b173a3f29482)

This is the difference of the result between before and after.
https://gist.github.com/yu-iskw/e7246041b173a3f29482/revisions

Author: Yu ISHIKAWA <yuu.ishikawa@gmail.com>

Closes #7440 from yu-iskw/SPARK-9052 and squashes the following commits:

015d738 [Yu ISHIKAWA] Fix the indentations and move the placement of commna
5cc30fe [Yu ISHIKAWA] Fix the indentation in a condition
4ead0e5 [Yu ISHIKAWA] [SPARK-9052][SparkR] Fix comments after curly braces

[[SPARK-9093] Fix single-quotes strings in SparkR - ASF JIRA](https://issues.apache.org/jira/browse/SPARK-9093)

This is the result of lintr at the rivision:01155162
[[SPARK-9093] The result of lintr at 01155162](https://gist.github.com/yu-iskw/8c47acf3202796da4d01)

Author: Yu ISHIKAWA <yuu.ishikawa@gmail.com>

Closes #7439 from yu-iskw/SPARK-9093 and squashes the following commits:

61c391e [Yu ISHIKAWA] [SPARK-9093][SparkR] Fix single-quotes strings in SparkR

JIRA: https://issues.apache.org/jira/browse/SPARK-8807

Add between operator in SparkR.

Author: Liang-Chi Hsieh <viirya@appier.com>

Closes #7356 from viirya/add_r_between and squashes the following commits:

7f51b44 [Liang-Chi Hsieh] Add test for non-numeric column.
c6a25c5 [Liang-Chi Hsieh] Add between function.

JIRA: https://issues.apache.org/jira/browse/SPARK-8840

Currently the type coercion rules don't include float type. This PR simply adds it.

Author: Liang-Chi Hsieh <viirya@appier.com>

Closes #7280 from viirya/add_r_float_coercion and squashes the following commits:

c86dc0e [Liang-Chi Hsieh] For comments.
dbf0c1b [Liang-Chi Hsieh] Implicitly convert Double to Float based on provided schema.
733015a [Liang-Chi Hsieh] Add test case for DataFrame with float type.
30c2a40 [Liang-Chi Hsieh] Update test case.
52b5294 [Liang-Chi Hsieh] Merge remote-tracking branch 'upstream/master' into add_r_float_coercion
6f9159d [Liang-Chi Hsieh] Add another test case.
8db3244 [Liang-Chi Hsieh] schema also needs to support float. add test case.
0dcc992 [Liang-Chi Hsieh] Add float coercion on SparkR.

Author: Sun Rui <rui.sun@intel.com>

Closes #7395 from sun-rui/SPARK-8808 and squashes the following commits:

ce603bc [Sun Rui] Use '<-' instead of '='.
88590b1 [Sun Rui] Use '<-' instead of '='.

This PR enables SparkR to dynamically ship the SparkR binary package to the AM node in YARN cluster mode, thus it is no longer required that the SparkR package be installed on each worker node.

This PR uses the JDK jar tool to package the SparkR package, because jar is thought to be available on both Linux/Windows platforms where JDK has been installed.

This PR does not address the R worker involved in RDD API. Will address it in a separate JIRA issue.

This PR does not address SBT build. SparkR installation and packaging by SBT will be addressed in a separate JIRA issue.

R/install-dev.bat is not tested. shivaram , Could you help to test it?

Author: Sun Rui <rui.sun@intel.com>

Closes #6743 from sun-rui/SPARK-6797 and squashes the following commits:

ca63c86 [Sun Rui] Adjust MimaExcludes after rebase.
7313374 [Sun Rui] Fix unit test errors.
72695fb [Sun Rui] Fix unit test failures.
193882f [Sun Rui] Fix Mima test error.
fe25a33 [Sun Rui] Fix Mima test error.
35ecfa3 [Sun Rui] Fix comments.
c38a005 [Sun Rui] Unzipped SparkR binary package is still required for standalone and Mesos modes.
b05340c [Sun Rui] Fix scala style.
2ca5048 [Sun Rui] Fix comments.
1acefd1 [Sun Rui] Fix scala style.
0aa1e97 [Sun Rui] Fix scala style.
41d4f17 [Sun Rui] Add support for locating SparkR package for R workers required by RDD APIs.
49ff948 [Sun Rui] Invoke jar.exe with full path in install-dev.bat.
7b916c5 [Sun Rui] Use 'rem' consistently.
3bed438 [Sun Rui] Add a comment.
681afb0 [Sun Rui] Fix a bug that RRunner does not handle client deployment modes.
cedfbe2 [Sun Rui] [SPARK-6797][SPARKR] Add support for YARN cluster mode.

JIRA: https://issues.apache.org/jira/browse/SPARK-8940

The given `schema` parameter will be overwritten in `createDataFrame` now. If it is not null, we shouldn't overwrite it.

Author: Liang-Chi Hsieh <viirya@appier.com>

Closes #7311 from viirya/df_not_overwrite_schema and squashes the following commits:

2385139 [Liang-Chi Hsieh] Don't overwrite given schema if it is not null.

Just change the attribute from -PsparkR to -Psparkr

Author: Dirceu Semighini Filho <dirceu.semighini@gmail.com>

Closes #7242 from dirceusemighini/patch-1 and squashes the following commits:

fad5991 [Dirceu Semighini Filho] Small update in the readme file

[[SPARK-8549] Fix the line length of SparkR - ASF JIRA](https://issues.apache.org/jira/browse/SPARK-8549)

Author: Yu ISHIKAWA <yuu.ishikawa@gmail.com>

Closes #7204 from yu-iskw/SPARK-8549 and squashes the following commits:

6fb131a [Yu ISHIKAWA] Fix the typo
1737598 [Yu ISHIKAWA] [SPARK-8549][SparkR] Fix the line length of SparkR

I've updated default values in comments, documentation, and in the command line builder to be 1g based on comments in the JIRA. I've also updated most usages to point at a single variable defined in the Utils.scala and JavaUtils.java files. This wasn't possible in all cases (R, shell scripts etc.) but usage in most code is now pointing at the same place.

Please let me know if I've missed anything.

Will the spark-shell use the value within the command line builder during instantiation?

Author: Ilya Ganelin <ilya.ganelin@capitalone.com>

Closes #7132 from ilganeli/SPARK-3071 and squashes the following commits:

4074164 [Ilya Ganelin] String fix
271610b [Ilya Ganelin] Merge branch 'SPARK-3071' of github.com:ilganeli/spark into SPARK-3071
273b6e9 [Ilya Ganelin] Test fix
fd67721 [Ilya Ganelin] Update JavaUtils.java
26cc177 [Ilya Ganelin] test fix
e5db35d [Ilya Ganelin] Fixed test failure
39732a1 [Ilya Ganelin] merge fix
a6f7deb [Ilya Ganelin] Created default value for DRIVER MEM in Utils that's now used in almost all locations instead of setting manually in each
09ad698 [Ilya Ganelin] Update SubmitRestProtocolSuite.scala
19b6f25 [Ilya Ganelin] Missed one doc update
2698a3d [Ilya Ganelin] Updated default value for driver memory

1. Update the pattern 'expect_true(a == b)' to 'expect_equal(a, b)'.
2. Update the pattern 'expect_true(inherits(a, b))' to 'expect_is(a, b)'.
3. Update the pattern 'expect_true(identical(a, b))' to 'expect_identical(a, b)'.

Author: Sun Rui <rui.sun@intel.com>

Closes #7152 from sun-rui/SPARK-7714 and squashes the following commits:

8ad2440 [Sun Rui] Fix test case errors.
8fe9f0c [Sun Rui] Update the pattern 'expect_true(identical(a, b))' to 'expect_identical(a, b)'.
f1b8005 [Sun Rui] Update the pattern 'expect_true(inherits(a, b))' to 'expect_is(a, b)'.
f631e94 [Sun Rui] Update the pattern 'expect_true(a == b)' to 'expect_equal(a, b)'.

Sometimes the user may want to show the complete content of cells. Now `sql("set -v").show()` displays:

![screen shot 2015-06-18 at 4 34 51 pm](https://cloud.githubusercontent.com/assets/1000778/8227339/14d3c5ea-15d9-11e5-99b9-f00b7e93beef.png)

The user needs to use something like `sql("set -v").collect().foreach(r => r.toSeq.mkString("\t"))` to show the complete content.

This PR adds a `pretty` parameter to show. If `pretty` is false, `show` won't truncate strings or align cells right.

![screen shot 2015-06-18 at 4 21 44 pm](https://cloud.githubusercontent.com/assets/1000778/8227407/b6f8dcac-15d9-11e5-8219-8079280d76fc.png)

Author: zsxwing <zsxwing@gmail.com>

Closes #6877 from zsxwing/show and squashes the following commits:

22e28e9 [zsxwing] pretty -> truncate
e582628 [zsxwing] Add pretty parameter to the show method in R
a3cd55b [zsxwing] Fix calling showString in R
923cee4 [zsxwing] Add a "pretty" parameter to show to display long strings

Add `getStaticClass` method in SparkR's `RBackendHandler`

This is a fix for the problem referenced in [SPARK-5185](https://issues.apache.org/jira/browse/SPARK-5185

).

cc shivaram

Author: cafreeman <cfreeman@alteryx.com>

Closes #7001 from cafreeman/branch-1.4 and squashes the following commits:

8f81194 [cafreeman] Add missing license
31aedcf [cafreeman] Refactor test to call an external R script
2c22073 [cafreeman] Merge branch 'branch-1.4' of github.com:apache/spark into branch-1.4
0bea809 [cafreeman] Fixed relative path issue and added smaller JAR
ee25e60 [cafreeman] Merge branch 'branch-1.4' of github.com:apache/spark into branch-1.4
9a5c362 [cafreeman] test for including JAR when launching sparkContext
9101223 [cafreeman] Merge branch 'branch-1.4' of github.com:apache/spark into branch-1.4
5a80844 [cafreeman] Fix style nits
7c6bd0c [cafreeman] [SPARK-8607] SparkR

(cherry picked from commit 2579948b)
Signed-off-by: Shivaram Venkataraman <shivaram@cs.berkeley.edu>

Test `infer_type` using a more fine-grained approach rather than comparing environments. Since `all.equal`'s behavior has changed in R 3.2, the test became unpassable.

JIRA here:
https://issues.apache.org/jira/browse/SPARK-8662



Author: cafreeman <cfreeman@alteryx.com>

Closes #7045 from cafreeman/R32_Test and squashes the following commits:

b97cc52 [cafreeman] Add `checkStructField` utility
3381e5c [cafreeman] Update SparkSQL Test

(cherry picked from commit 78b31a2a)
Signed-off-by: Shivaram Venkataraman <shivaram@cs.berkeley.edu>

cc cafreeman

Author: Shivaram Venkataraman <shivaram@cs.berkeley.edu>

Closes #7022 from shivaram/sparkr-init-hotfix and squashes the following commits:

9178d15 [Shivaram Venkataraman] Fix packages argument, sparkSubmitBinName

Author: Holden Karau <holden@pigscanfly.ca>

Closes #6928 from holdenk/SPARK-8506-sparkr-does-not-provide-an-easy-way-to-depend-on-spark-packages-when-performing-init-from-inside-of-r and squashes the following commits:

b60dd63 [Holden Karau] Add an example with the spark-csv package
fa8bc92 [Holden Karau] typo: sparm -> spark
865a90c [Holden Karau] strip spaces for comparision
c7a4471 [Holden Karau] Add some documentation
c1a9233 [Holden Karau] refactor for testing
c818556 [Holden Karau] Add pakages to R

spark version is taken from the environment variable SPARK_VERSION

Author: Alok  Singh <singhal@Aloks-MacBook-Pro.local>
Author: Alok  Singh <singhal@aloks-mbp.usca.ibm.com>

Closes #6944 from aloknsingh/aloknsingh_spark_jiras and squashes the following commits:

ed607bd [Alok  Singh] [SPARK-8111][SparkR] As per suggestion, 1) using the version from sparkContext rather than the Sys.env. 2) change "Welcome to SparkR!" to "Welcome to" followed by Spark logo and version
acd5b85 [Alok  Singh] fix the jira SPARK-8111 to add the spark version and logo. Currently spark version is taken from the environment variable SPARK_VERSION

[[SPARK-8431] Add in operator to DataFrame Column in SparkR - ASF JIRA](https://issues.apache.org/jira/browse/SPARK-8431)

Author: Yu ISHIKAWA <yuu.ishikawa@gmail.com>

Closes #6941 from yu-iskw/SPARK-8431 and squashes the following commits:

1f64423 [Yu ISHIKAWA] Modify the comment
f4309a7 [Yu ISHIKAWA] Make a `setMethod` for `%in%` be independent
6e37936 [Yu ISHIKAWA] Modify a variable name
c196173 [Yu ISHIKAWA] [SPARK-8431][SparkR] Add in operator to DataFrame Column in SparkR

[[SPARK-8548] Remove the trailing whitespaces from the SparkR files - ASF JIRA](https://issues.apache.org/jira/browse/SPARK-8548)

- This is the result of `lint-r`
    https://gist.github.com/yu-iskw/0019b37a2c1167f33986

Author: Yu ISHIKAWA <yuu.ishikawa@gmail.com>

Closes #6945 from yu-iskw/SPARK-8548 and squashes the following commits:

0bd567a [Yu ISHIKAWA] [SPARK-8548][SparkR] Remove the trailing whitespaces from the SparkR files

[[SPARK-8537] Add a validation rule about the curly braces in SparkR to `.lintr` - ASF JIRA](https://issues.apache.org/jira/browse/SPARK-8537)

Author: Yu ISHIKAWA <yuu.ishikawa@gmail.com>

Closes #6940 from yu-iskw/SPARK-8537 and squashes the following commits:

7eec1a0 [Yu ISHIKAWA] [SPARK-8537][SparkR] Add a validation rule about the curly braces in SparkR to `.lintr`

Thank Shivaram Venkataraman for your support. This is a prototype script to validate the R files.

Author: Yu ISHIKAWA <yuu.ishikawa@gmail.com>

Closes #6922 from yu-iskw/SPARK-6813 and squashes the following commits:

c1ffe6b [Yu ISHIKAWA] Modify to save result to a log file and add a rule to validate
5520806 [Yu ISHIKAWA] Exclude the .lintr file not to check Apache lincence
8f94680 [Yu ISHIKAWA] [SPARK-8495][SparkR] Add a `.lintr` file to validate the SparkR files and the `lint-r` script

This pull request adds following methods to SparkR:

```R
setJobGroup()
cancelJobGroup()
clearJobGroup()
```
For each method, the spark context is passed as the first argument. There does not seem to be a good way to test these in R.

cc shivaram and davies

Author: Hossein <hossein@databricks.com>

Closes #6889 from falaki/SPARK-8452 and squashes the following commits:

9ce9f1e [Hossein] Added basic tests to verify methods can be called and won't throw errors
c706af9 [Hossein] Added examples
a2c19af [Hossein] taking spark context as first argument
343ca77 [Hossein] Added setJobGroup, cancelJobGroup and clearJobGroup to SparkR

Right now it's logged to "R-unit-tests.log". Jenkins currently only archives files named "unit-tests.log", and this is what all other modules (e.g. SQL, network, REPL) use.
1. We should be consistent
2. I don't want to reconfigure Jenkins to accept a different file

shivaram

Author: andrewor14 <andrew@databricks.com>
Author: Andrew Or <andrew@databricks.com>

Closes #6807 from andrewor14/r-logs and squashes the following commits:

96005d2 [andrewor14] Nest unit-tests.log further until R
407c46c [andrewor14] Add target to log path
d7b68ae [Andrew Or] Log R unit test output to "unit-tests.log"

Author: hqzizania <qian.huang@intel.com>

Closes #6190 from hqzizania/R and squashes the following commits:

1641f9e [hqzizania] fixes and add test units
bb3411a [hqzizania] Convert NAs to null type in SparkR DataFrames

cc davies sun-rui

Author: Shivaram Venkataraman <shivaram@cs.berkeley.edu>

Closes #6620 from shivaram/sparkr-read-schema and squashes the following commits:

16a6726 [Shivaram Venkataraman] Fix loadDF to pass schema Also add a unit test
a229877 [Shivaram Venkataraman] Use wrapper function to DataFrameReader
ee70ba8 [Shivaram Venkataraman] Support user-specified schema in read.df

This also helps us get rid of the sparkr-docs maven profile as docs are now built by just using -Psparkr when the roxygen2 package is available

Related to discussion in #6567

cc pwendell srowen -- Let me know if this looks better

Author: Shivaram Venkataraman <shivaram@cs.berkeley.edu>

Closes #6593 from shivaram/sparkr-pom-cleanup and squashes the following commits:

b282241 [Shivaram Venkataraman] Remove sparkr-docs from release script as well
8f100a5 [Shivaram Venkataraman] Move man pages creation to install-dev.sh This also helps us get rid of the sparkr-docs maven profile as docs are now built by just using -Psparkr when the roxygen2 package is available

cc shaneknapp pwendell JoshRosen

Author: Shivaram Venkataraman <shivaram@cs.berkeley.edu>

Closes #6623 from shivaram/SPARK-8084 and squashes the following commits:

0ec5b26 [Shivaram Venkataraman] Make SparkR scripts fail on error

[SPARK-8063] [SPARKR] Spark master URL conflict between MASTER env variable and --master command line option.

Author: Sun Rui <rui.sun@intel.com>

Closes #6605 from sun-rui/SPARK-8063 and squashes the following commits:

51ca48b [Sun Rui] [SPARK-8063][SPARKR] Spark master URL conflict between MASTER env variable and --master command line option.

Author: Sun Rui <rui.sun@intel.com>

Closes #6183 from sun-rui/SPARK-7227 and squashes the following commits:

dd6f5b3 [Sun Rui] Rename readEnv() back to readMap(). Add alias na.omit() for dropna().
41cf725 [Sun Rui] [SPARK-7227][SPARKR] Support fillna / dropna in R DataFrame.

cc davies

Author: Shivaram Venkataraman <shivaram@cs.berkeley.edu>

Closes #6507 from shivaram/sparkr-init and squashes the following commits:

6fdd169 [Shivaram Venkataraman] Create SparkContext in sparkRSQL init

This PR adds a new SparkR programming guide at the top-level. This will be useful for R users as our APIs don't directly match the Scala/Python APIs and as we need to explain SparkR without using RDDs as examples etc.

cc rxin davies pwendell

cc cafreeman -- Would be great if you could also take a look at this !

Author: Shivaram Venkataraman <shivaram@cs.berkeley.edu>

Closes #6490 from shivaram/sparkr-guide and squashes the following commits:

d5ff360 [Shivaram Venkataraman] Add a section on HiveContext, HQL queries
408dce5 [Shivaram Venkataraman] Fix link
dbb86e3 [Shivaram Venkataraman] Fix minor typo
9aff5e0 [Shivaram Venkataraman] Address comments, use dplyr-like syntax in example
d09703c [Shivaram Venkataraman] Fix default argument in read.df
ea816a1 [Shivaram Venkataraman] Add a new SparkR programming guide Also update write.df, read.df to handle defaults better

This change also remove native libraries from SparkR to make sure our distribution works across platforms

Tested by building on Mac, running on Amazon Linux (CentOS), Windows VM and vice-versa (built on Linux run on Mac)

I will also test this with YARN soon and update this PR.

Author: Shivaram Venkataraman <shivaram@cs.berkeley.edu>

Closes #6373 from shivaram/sparkr-binary and squashes the following commits:

ae41b5c [Shivaram Venkataraman] Remove native libraries from SparkR Also include the built SparkR package in make-distribution.sh

sqlCtx -> sqlContext

You can check the docs by:

```
$ cd docs
$ SKIP_SCALADOC=1 jekyll serve
```
cc shivaram

Author: Davies Liu <davies@databricks.com>

Closes #5442 from davies/r_docs and squashes the following commits:

7a12ec6 [Davies Liu] remove rdd in R docs
8496b26 [Davies Liu] remove the docs related to RDD
e23b9d6 [Davies Liu] delete R docs for RDD API
222e4ff [Davies Liu] Merge branch 'master' into r_docs
89684ce [Davies Liu] Merge branch 'r_docs' of github.com:davies/spark into r_docs
f0a10e1 [Davies Liu] address comments from @shivaram
f61de71 [Davies Liu] Update pairRDD.R
3ef7cf3 [Davies Liu] use + instead of function(a,b) a+b
2f10a77 [Davies Liu] address comments from @cafreeman
9c2a062 [Davies Liu] mention R api together with Python API
23f751a [Davies Liu] Fill in SparkR examples in programming guide

In `DataFrame.describe()`, the `count` aggregate produces an integer, the `avg` and `stdev` aggregates produce doubles, and `min` and `max` aggregates can produce varying types depending on what type of column they're applied to.  As a result, we should cast all aggregate results to String so that `describe()`'s output types match its declared output schema.

Author: Josh Rosen <joshrosen@databricks.com>

Closes #6218 from JoshRosen/SPARK-7687 and squashes the following commits:

146b615 [Josh Rosen] Fix R test.
2974bd5 [Josh Rosen] Cast to string type instead
f206580 [Josh Rosen] Cast to double to fix SPARK-7687
307ecbf [Josh Rosen] Add failing regression test for SPARK-7687

Author: qhuang <qian.huang@intel.com>

Closes #6170 from hqzizania/master and squashes the following commits:

f20c39f [qhuang] add tests units and fixes
2a7d121 [qhuang] use a function name more familiar to R users
07aa72e [qhuang] Support math functions in R DataFrame

[SPARK-7482] [SPARKR] Rename some DataFrame API methods in SparkR to match their counterparts in Scala.

Author: Sun Rui <rui.sun@intel.com>

Closes #6007 from sun-rui/SPARK-7482 and squashes the following commits:

5c5cf5e [Sun Rui] Implement alias loadDF() as a new function.
3a30c10 [Sun Rui] Rename load()/save() to read.df()/write.df(). Also add loadDF()/saveDF() as aliases.
9f569d6 [Sun Rui] [SPARK-7482][SparkR] Rename some DataFrame API methods in SparkR to match their counterparts in Scala.