解惑rJava R与Java的快速通道

阅读导读：

1.什么是RJava？

2.怎样安装RJava？

3.怎样用RJava实现R调用Java？

1.
rJava介绍

rJava是一个R语言和Java语言的通信接口。通过底层JNI实现调用，同意在R中直接调用Java的对象和方法。

rJava还提供了Java调用R的功能，是通过JRI(Java/R Interface)实现的。

JRI如今已经被嵌入到rJava的包中，我们也能够单独试用这个功能。如今rJava包。已经成为非常多基于Java开发R包的基础功能组件。

正式因为rJava是底层接口，并使用JNI作为接口调用，所以效率很高。在JRI的方案中，JVM直接通过内存直接载入RVM。调用过程性能差点儿无损耗。因此是很高效连接通道，是R和Java通信的首选开发包。

2.
rJava安装

系统环境：

Linux Ubuntu 12.04.2 LTS 64bit server
R version 3.0.1 64bit
Java (Oracle SUN) 1.6.0_29 64bit Server VM

~ uname -a

Linux conan 3.5.0-23-generic #35~precise1-Ubuntu SMP Fri Jan 25 17:13:26 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux

~ cat /etc/issue

Ubuntu 12.04.2 LTS \n \l

~ R --version

R version 3.0.1 (2013-05-16) -- "Good Sport"

Copyright (C) 2013 The R Foundation for Statistical Computing

Platform: x86_64-pc-linux-gnu (64-bit)

R is free software and comes with ABSOLUTELY NO WARRANTY.

You are welcome to redistribute it under the terms of the

GNU General Public License versions 2 or 3.

For more information about these matters see

http://www.gnu.org/licenses/.

~ java -version

java version "1.6.0_29"

Java(TM) SE Runtime Environment (build 1.6.0_29-b11)

Java HotSpot(TM) 64-Bit Server VM (build 20.4-b02, mixed mode)

rJava安装

#配置rJava环境

~ sudo R CMD javareconf

#启动R

~ sudo R

> install.packages("rJava")

installing via 'install.libs.R' to /usr/local/lib/R/site-library/rJava

** R

** inst

** preparing package for lazy loading

** help

*** installing help indices

** building package indices

** testing if installed package can be loaded

* DONE (rJava)

The downloaded source packages are in

‘/tmp/RtmpiZyCE7/downloaded_packages’

3.
rJava实现R调用Java

在R环境中。使用rJava包编程

#载入rJava包

> library(rJava)

> search()

[1] ".GlobalEnv"       "package:rJava"    "package:stats"

[4] "package:graphics"  "package:grDevices" "package:utils"

[7] "package:datasets"  "package:methods" "Autoloads"

[10] "package:base"

#启动JVM

> .jinit()

#声明并赋值到字符串

> s <- .jnew("java/lang/String", "Hello World!")

> s

[1] "Java-Object{Hello World!}"

#查看字符串长度

> .jcall(s,"I","length")

[1] 12

#索引World的位置

> .jcall(s,"I","indexOf","World")

[1] 6

#查看concat的方法声明

> .jmethods(s,"concat")

[1] "public java.lang.String java.lang.String.concat(java.lang.String)"

#使用concat方法连接字符串

> .jcall(s,"Ljava/lang/String;","concat",s)

[1] "Hello World!Hello World!"

#打印字符串对象

> print(s)

[1] "Java-Object{Hello World!}"

#打印字符串值

> .jstrVal(s)

[1] "Hello World!"

rJava优化过的方法调用。用$来调用方法

#同.jcall(s,"I","length")

> s$length()

[1] 12

#同.jcall(s,"I","indexOf","World")

> s$indexOf("World")

[1] 6

4. rJava(JRI)实现Java调用R (win7)

在win7中安装rJava

系统环境：

win7 64bit 旗舰版
R 3.0.1
Java 1.6.0_45

环境变量设置

PATH: C:\Program Files\R\R-3.0.1\bin\x64;D:\toolkit\java\jdk6\bin;;D:\toolkit\java\jdk6\jre\bin\server

JAVA_HOME: D:\toolkit\java\jdk6

CLASSPATH: C:\Program Files\R\R-3.0.1\library\rJava\jri

在R中安装rJava

> install.packages("rJava")

#载入rJava

> library(rJava)

> .jinit()

#R调用Java变量測试

> s <- .jnew("java/lang/String", "Hello World!")

> s

[1] "Java-Object{Hello World!}"

启动Eclipse编写程

package org.conan.r.rjava;

import org.rosuda.JRI.Rengine;

public class DemoRJava {

public static void main(String[] args) {

      DemoRJava demo = new DemoRJava();

      demo.callRJava();

}

public void callRJava() {

      Rengine re = new Rengine(new String[] { "--vanilla" }, false, null);

      if (!re.waitForR()) {

         System.out.println("Cannot load R");

         return;

      }



      //打印变量

      String version = re.eval("R.version.string").asString();

      System.out.println(version);

      //循环打印数组

      double[] arr = re.eval("rnorm(10)").asDoubleArray();

      for (double a : arr) {

         System.out.print(a + ",");

      }

      re.end();

}

}

在Eclipse启动设置VM參数：

-Djava.library.path="C:\Program Files\R\R-3.0.1\library\rJava\jri\x64"

mod=image&aid=9234&size=300x300&key=c3fb7cbb1d59469d&nocache=yes&type=fixnone" border="0" width="300" alt="" style="margin:0px; padding:0px; word-wrap:break-word; max-width:400px; color:rgb(68,68,68); font-family:Tahoma,'Microsoft Yahei',Simsun; font-size:14px; line-height:21px">

执行结果：

R version 3.0.1 (2013-05-16)

0.04051018703700011,-0.3321596519938258,0.45642459001166913,-1.1907153494936031,1.5872266854172385,1.3639721994863943,-0.6309712627586983,-1.5226698569087498,-1.0416402147174952,0.4864034017637044,

打包DemoRJava.jar

在Eclipse中完毕打包，上传到linux环境，继续測试。

5.
rJava(JRI)实现Java调用R (Ubuntu)

新建文件夹DemoRJava，上传DemoRJava.jar到DemoRJava

~ mkdir /home/conan/R/DemoRJava

~ cd /home/conan/R/DemoRJava

~ ls -l

-rw-r--r-- 1 conan conan 1328 Aug 8 2013 DemoRJava.jar

执行Jar包

~ export R_HOME=/usr/lib/R

~ java -Djava.library.path=/usr/local/lib/R/site-library/rJava/jri -cp /usr/local/lib/R/site-library/rJava/jri/JRI.jar:/home/conan/R/DemoRJava/DemoRJava.jar org.conan.r.rjava.DemoRJava

执行结果

R version 3.0.1 (2013-05-16)

0.6374494596732511,1.3413824702002808,0.04573045670001342,-0.6885617932810327,0.14970067632722675,-0.3989493870007832,-0.6148250252955993,0.40132038323714453,-0.5385260423222166,0.3459850956295771,

我们完毕了。R和Java的互调。

包含了R通过rJava调用Java，Java通过JRI调用R。

并演示了win和linux中的用法。

巴特西

解惑rJava R与Java的快速通道

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