JAVA 调用 R 语言

1 简介

R是统计计算的强大工具，而JAVA是做应用系统的主流语言，两者天然具有整合的需要。关于整合，一方面，R中可以创建JAVA对象调用JAVA方法，另一方面，JAVA中可以转换R的数据类型调用R的函数，互相取长补短。现在也有一个项目JGR，用JAVA做R的图形界面，可以实现高亮显示自动补全等，还能让JAVA和R互相调用。

关于R中调用JAVA，我想主要是为了利用其面向对象的特性，毕竟R语言近来很致力于向面向对象发展，有个很好的项目rJava可以实现，在www.rforge.net/rJava上。R中调JAVA对我似乎意义不大，本文主要介绍JAVA中调用R。

　JAVA很适合开发应用系统，但是数学建模和计算能力非其所长，如果该系统需要进行大量的统计或者优化的计算，调用R是一种很好的方式。JAVA负责系统的构建，R用来做运算引擎，从而实现应用型和分析性相结合的系统。

目前网上有两种方式使用java调用R。

2       Rserve的方式

2.1     介绍

首先要介绍的是Rserve的方式，这是一个基于TCP/IP的服务器，通过二进制协议传输数据，可以提供远程连接，使得客户端语言能够调用R。目前Rserve作为一个package发布在CRAN上，可以直接使用install.packages("Rserve")进行安装。需要使用时在R控制台下加载该包，然后输入命令Rserve()，开启服务器，就可以供客户端调用。

其客户端可以有多种，这里只介绍JAVA客户端。最早的客户端包是JRclient，在www.rosuda.org/Rserve上还可以下载到，但是现在该项目全部移到了www.rforge.net/Rserve，使用REngine作客户端（和JRI一致），在该网站下可以下载到REngine.jar和RserveEngine.jar两个文件。如果用eclipse开发的话，在工程属性中导入这两个外部的jar包，就可以正常使用了。

首先建立一个新的连接，然后就可以使用eval之类的方法将R中的表达式传到服务器端，通过R求值后传回JAVA中REXP类型的变量，然后打印出来，整个过程非常简单。由于不需要对R进行初始化，因此速度会比较快。在其他系统下可以同时建立多个连接，但是在Windows下只允许同时打开一个连接，后续的连接都会共有相同的命名空间。官网上不建议在Windows下使用Rserve，因为会丧失很多性能，他们推荐可以考虑DCOM的方式。不过DCOM那个工程没有现成的jar包可用，其实如果是拿R做分析系统中的运算引擎，单连接够用了。

2.2     操作步骤

(一)   在R里下载“Rserve”包，并安装

安装好后，

运行如下命令启动“Rserver”

> library(Rserve)

> Rserve()

Starting Rserve...

"D:\PROGRA~1\R\R-30~1.1\library\Rserve\libs\i386\Rserve.exe"

>

(二)   建立java工程，导入必要的包，写出测试用例

目录结构如下（标红色的是需要的）：

Test.java 内容

package com.rTest;

import org.rosuda.REngine.REXP;

import org.rosuda.REngine.Rserve.RConnection;

public class Test {

public static void main(String[] args) {

try {

RConnection c = new RConnection();

REXP x = c.eval("R.version.string");

System.out.println(x.asString());

} catch (Exception e) {

e.printStackTrace();

}

}

}

运行即可

2.3     可能出现的错误

2.3.1  Connection refused: connect

org.rosuda.REngine.Rserve.RserveException: Cannot connect: Connection refused: connect

at org.rosuda.REngine.Rserve.RConnection.<init>(RConnection.java:88)

at org.rosuda.REngine.Rserve.RConnection.<init>(RConnection.java:60)

at org.rosuda.REngine.Rserve.RConnection.<init>(RConnection.java:44)

at com.rTest.Test.main(Test.java:9)

这是由于“Rserve” 服务器没有启动起来的原因，试试在R内运行如下语句

> library(Rserve)

> Rserve()

3       JRI 的方式

3.1     介绍

另一种方式是JRI，全名是Java/R Interface，这是一种完全不同的方式，通过调用R的动态链接库从而利用R中的函数等。目前该项目已经成了rJava的子项目，不再提供单独的JRI的版本。因此使用时简单地通过install.packages("rJava")安装rJava就行，在安装文件夹中，可以看到一个jri的子文件夹，里面有自带的例子可以用来测试。

装好后要修改系统的环境变量，在PATH中添加%R_HOME%/bin和%R_HOME%/library/rJava/jri，注意R_HOME的路径要正确，重启系统使之生效。使用时同样在eclipse里导入外部的jar包（在www.rforge.net/rJava下载JRI.jar、REngine.jar和JRIEngine.jar这三个文件），在rJava包安装目录下的jri/examples里有现成的例子（rtest.java和rtest2.java），可以测试是否成功。

3.2     操作步骤

(一)   在R中下载安装“Rjava”包

(二)   配置环境变量

我自己的path如下：

D:\Program Files\Java\jdk1.7.0_09\bin;D:\Program Files\R\R-3.0.1\bin\i386;D:\Program Files\R\R-3.0.1\library\rJava\jri;D:\Program Files\R\R-3.0.1\library\rJava\jri\i386

(三)   建立java工程

标红线的是必须的

Rtest 和Rest2 都是Rjava例子里的

package com.rTest;

import java.io.*;

import java.awt.Frame;

import java.awt.FileDialog;

import java.util.Enumeration;

import org.rosuda.JRI.Rengine;

import org.rosuda.JRI.REXP;

import org.rosuda.JRI.RList;

import org.rosuda.JRI.RVector;

import org.rosuda.JRI.RMainLoopCallbacks;

class TextConsole implements RMainLoopCallbacks

{

public void rWriteConsole(Rengine re, String text, int oType) {

System.out.print(text);

}

public void rBusy(Rengine re, int which) {

System.out.println("rBusy("+which+")");

}

public String rReadConsole(Rengine re, String prompt, int addToHistory) {

System.out.print(prompt);

try {

BufferedReader br=new BufferedReader(new InputStreamReader(System.in));

String s=br.readLine();

return (s==null||s.length()==0)?s:s+"\n";

} catch (Exception e) {

System.out.println("jriReadConsole exception: "+e.getMessage());

}

return null;

}

public void rShowMessage(Rengine re, String message) {

System.out.println("rShowMessage \""+message+"\"");

}

public String rChooseFile(Rengine re, int newFile) {

FileDialog fd = new FileDialog(new Frame(), (newFile==0)?"Select a file":"Select a new file", (newFile==0)?FileDialog.LOAD:FileDialog.SAVE);

fd.show();

String res=null;

if (fd.getDirectory()!=null) res=fd.getDirectory();

if (fd.getFile()!=null) res=(res==null)?fd.getFile():(res+fd.getFile());

return res;

}

public void   rFlushConsole (Rengine re) {

}

public void   rLoadHistory  (Rengine re, String filename) {

}

public void   rSaveHistory  (Rengine re, String filename) {

}

}

public class rtest {

public static void main(String[] args) {

// just making sure we have the right version of everything

if (!Rengine.versionCheck()) {

System.err.println("** Version mismatch - Java files don't match library version.");

System.exit(1);

}

System.out.println("Creating Rengine (with arguments)");

// 1) we pass the arguments from the command line

// 2) we won't use the main loop at first, we'll start it later

//    (that's the "false" as second argument)

// 3) the callbacks are implemented by the TextConsole class above

Rengine re=new Rengine(args, false, new TextConsole());

System.out.println("Rengine created, waiting for R");

// the engine creates R is a new thread, so we should wait until it's ready

if (!re.waitForR()) {

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

return;

}

/* High-level API - do not use RNI methods unless there is no other way

to accomplish what you want */

try {

REXP x;

re.eval("data(iris)",false);

System.out.println(x=re.eval("iris"));

// generic vectors are RVector to accomodate names

RVector v = x.asVector();

if (v.getNames()!=null) {

System.out.println("has names:");

for (Enumeration e = v.getNames().elements() ; e.hasMoreElements() ;) {

System.out.println(e.nextElement());

}

}

// for compatibility with Rserve we allow casting of vectors to lists

RList vl = x.asList();

String[] k = vl.keys();

if (k!=null) {

System.out.println("and once again from the list:");

int i=0; while (i<k.length) System.out.println(k[i++]);

}

// get boolean array

System.out.println(x=re.eval("iris[[1]]>mean(iris[[1]])"));

// R knows about TRUE/FALSE/NA, so we cannot use boolean[] this way

// instead, we use int[] which is more convenient (and what R uses internally anyway)

int[] bi = x.asIntArray();

{

int i = 0; while (i<bi.length) { System.out.print(bi[i]==0?"F ":(bi[i]==1?"T ":"NA ")); i++; }

System.out.println("");

}

// push a boolean array

boolean by[] = { true, false, false };

re.assign("bool", by);

System.out.println(x=re.eval("bool"));

// asBool returns the first element of the array as RBool

// (mostly useful for boolean arrays of the length 1). is should return true

System.out.println("isTRUE? "+x.asBool().isTRUE());

// now for a real dotted-pair list:

System.out.println(x=re.eval("pairlist(a=1,b='foo',c=1:5)"));

RList l = x.asList();

if (l!=null) {

int i=0;

String [] a = l.keys();

System.out.println("Keys:");

while (i<a.length) System.out.println(a[i++]);

System.out.println("Contents:");

i=0;

while (i<a.length) System.out.println(l.at(i++));

}

System.out.println(re.eval("sqrt(36)"));

} catch (Exception e) {

System.out.println("EX:"+e);

e.printStackTrace();

}

// Part 2 - low-level API - for illustration purposes only!

//System.exit(0);

// simple assignment like a<-"hello" (env=0 means use R_GlobalEnv)

long xp1 = re.rniPutString("hello");

re.rniAssign("a", xp1, 0);

// Example: how to create a named list or data.frame

double da[] = {1.2, 2.3, 4.5};

double db[] = {1.4, 2.6, 4.2};

long xp3 = re.rniPutDoubleArray(da);

long xp4 = re.rniPutDoubleArray(db);

// now build a list (generic vector is how that's called in R)

long la[] = {xp3, xp4};

long xp5 = re.rniPutVector(la);

// now let's add names

String sa[] = {"a","b"};

long xp2 = re.rniPutStringArray(sa);

re.rniSetAttr(xp5, "names", xp2);

// ok, we have a proper list now

// we could use assign and then eval "b<-data.frame(b)", but for now let's build it by hand:

String rn[] = {"1", "2", "3"};

long xp7 = re.rniPutStringArray(rn);

re.rniSetAttr(xp5, "row.names", xp7);

long xp6 = re.rniPutString("data.frame");

re.rniSetAttr(xp5, "class", xp6);

// assign the whole thing to the "b" variable

re.rniAssign("b", xp5, 0);

{

System.out.println("Parsing");

long e=re.rniParse("data(iris)", 1);

System.out.println("Result = "+e+", running eval");

long r=re.rniEval(e, 0);

System.out.println("Result = "+r+", building REXP");

REXP x=new REXP(re, r);

System.out.println("REXP result = "+x);

}

{

System.out.println("Parsing");

long e=re.rniParse("iris", 1);

System.out.println("Result = "+e+", running eval");

long r=re.rniEval(e, 0);

System.out.println("Result = "+r+", building REXP");

REXP x=new REXP(re, r);

System.out.println("REXP result = "+x);

}

{

System.out.println("Parsing");

long e=re.rniParse("names(iris)", 1);

System.out.println("Result = "+e+", running eval");

long r=re.rniEval(e, 0);

System.out.println("Result = "+r+", building REXP");

REXP x=new REXP(re, r);

System.out.println("REXP result = "+x);

String s[]=x.asStringArray();

if (s!=null) {

int i=0; while (i<s.length) { System.out.println("["+i+"] \""+s[i]+"\""); i++; }

}

}

{

System.out.println("Parsing");

long e=re.rniParse("rnorm(10)", 1);

System.out.println("Result = "+e+", running eval");

long r=re.rniEval(e, 0);

System.out.println("Result = "+r+", building REXP");

REXP x=new REXP(re, r);

System.out.println("REXP result = "+x);

double d[]=x.asDoubleArray();

if (d!=null) {

int i=0; while (i<d.length) { System.out.print(((i==0)?"":", ")+d[i]); i++; }

System.out.println("");

}

System.out.println("");

}

{

REXP x=re.eval("1:10");

System.out.println("REXP result = "+x);

int d[]=x.asIntArray();

if (d!=null) {

int i=0; while (i<d.length) { System.out.print(((i==0)?"":", ")+d[i]); i++; }

System.out.println("");

}

}

re.eval("print(1:10/3)");

if (true) {

// so far we used R as a computational slave without REPL

// now we start the loop, so the user can use the console

System.out.println("Now the console is yours ... have fun");

re.startMainLoop();

} else {

re.end();

System.out.println("end");

}

}

}

package com.rTest;

import java.io.*;

import java.awt.*;

import javax.swing.*;

import org.rosuda.JRI.Rengine;

import org.rosuda.JRI.REXP;

import org.rosuda.JRI.RMainLoopCallbacks;

import org.rosuda.JRI.RConsoleOutputStream;

class TextConsole2 implements RMainLoopCallbacks

{

JFrame f;

public JTextArea textarea = new JTextArea();

public TextConsole2() {

f = new JFrame();

f.getContentPane().add(new JScrollPane(textarea));

f.setSize(new Dimension(800,600));

f.show();

}

public void rWriteConsole(Rengine re, String text, int oType) {

textarea.append(text);

}

public void rBusy(Rengine re, int which) {

System.out.println("rBusy("+which+")");

}

public String rReadConsole(Rengine re, String prompt, int addToHistory) {

System.out.print(prompt);

try {

BufferedReader br=new BufferedReader(new InputStreamReader(System.in));

String s=br.readLine();

return (s==null||s.length()==0)?s:s+"\n";

} catch (Exception e) {

System.out.println("jriReadConsole exception: "+e.getMessage());

}

return null;

}

public void rShowMessage(Rengine re, String message) {

System.out.println("rShowMessage \""+message+"\"");

}

public String rChooseFile(Rengine re, int newFile) {

FileDialog fd = new FileDialog(f, (newFile==0)?"Select a file":"Select a new file", (newFile==0)?FileDialog.LOAD:FileDialog.SAVE);

fd.show();

String res=null;

if (fd.getDirectory()!=null) res=fd.getDirectory();

if (fd.getFile()!=null) res=(res==null)?fd.getFile():(res+fd.getFile());

return res;

}

public void   rFlushConsole (Rengine re) {

}

public void   rLoadHistory  (Rengine re, String filename) {

}

public void   rSaveHistory  (Rengine re, String filename) {

}

}

public class rtest2 {

public static void main(String[] args) {

System.out.println("Press <Enter> to continue (time to attach the debugger if necessary)");

try { System.in.read(); } catch(Exception e) {};

System.out.println("Creating Rengine (with arguments)");

Rengine re=new Rengine(args, true, new TextConsole2());

System.out.println("Rengine created, waiting for R");

if (!re.waitForR()) {

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

return;

}

System.out.println("re-routing stdout/err into R console");

System.setOut(new PrintStream(new RConsoleOutputStream(re, 0)));

System.setErr(new PrintStream(new RConsoleOutputStream(re, 1)));

System.out.println("Letting go; use main loop from now on");

}

}

运行即可 Rtest 运行结果如下：

Creating Rengine (with arguments)

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

Copyright (C) 2013 The R Foundation for Statistical Computing

Platform: i386-w64-mingw32/i386 (32-bit)

R is free software and comes with ABSOLUTELY NO WARRANTY.

You are welcome to redistribute it under certain conditions.

Type 'license()' or 'licence()' for distribution details.

R is a collaborative project with many contributors.

Type 'contributors()' for more information and

'citation()' on how to cite R or R packages in publications.

Type 'demo()' for some demos, 'help()' for on-line help, or

'help.start()' for an HTML browser interface to help.

Type 'q()' to quit R.

[1] "LC_COLLATE=Chinese_People's Republic of China.936;LC_CTYPE=Chinese_People's Republic of China.936;LC_MONETARY=Chinese_People's Republic of China.936;LC_NUMERIC=C;LC_TIME=Chinese_People's Republic of China.936"

Rengine created, waiting for R

[VECTOR ([REAL* (5.1, 4.9, 4.7, 4.6, 5.0, 5.4, 4.6, 5.0, 4.4, 4.9, 5.4, 4.8, 4.8, 4.3, 5.8, 5.7, 5.4, 5.1, 5.7, 5.1, 5.4, 5.1, 4.6, 5.1, 4.8, 5.0, 5.0, 5.2, 5.2, 4.7, 4.8, 5.4, 5.2, 5.5, 4.9, 5.0, 5.5, 4.9, 4.4, 5.1, 5.0, 4.5, 4.4, 5.0, 5.1, 4.8, 5.1, 4.6, 5.3, 5.0, 7.0, 6.4, 6.9, 5.5, 6.5, 5.7, 6.3, 4.9, 6.6, 5.2, 5.0, 5.9, 6.0, 6.1, 5.6, 6.7, 5.6, 5.8, 6.2, 5.6, 5.9, 6.1, 6.3, 6.1, 6.4, 6.6, 6.8, 6.7, 6.0, 5.7, 5.5, 5.5, 5.8, 6.0, 5.4, 6.0, 6.7, 6.3, 5.6, 5.5, 5.5, 6.1, 5.8, 5.0, 5.6, 5.7, 5.7, 6.2, 5.1, 5.7, ... (50 more values follow))], [REAL* (3.5, 3.0, 3.2, 3.1, 3.6, 3.9, 3.4, 3.4, 2.9, 3.1, 3.7, 3.4, 3.0, 3.0, 4.0, 4.4, 3.9, 3.5, 3.8, 3.8, 3.4, 3.7, 3.6, 3.3, 3.4, 3.0, 3.4, 3.5, 3.4, 3.2, 3.1, 3.4, 4.1, 4.2, 3.1, 3.2, 3.5, 3.6, 3.0, 3.4, 3.5, 2.3, 3.2, 3.5, 3.8, 3.0, 3.8, 3.2, 3.7, 3.3, 3.2, 3.2, 3.1, 2.3, 2.8, 2.8, 3.3, 2.4, 2.9, 2.7, 2.0, 3.0, 2.2, 2.9, 2.9, 3.1, 3.0, 2.7, 2.2, 2.5, 3.2, 2.8, 2.5, 2.8, 2.9, 3.0, 2.8, 3.0, 2.9, 2.6, 2.4, 2.4, 2.7, 2.7, 3.0, 3.4, 3.1, 2.3, 3.0, 2.5, 2.6, 3.0, 2.6, 2.3, 2.7, 3.0, 2.9, 2.9, 2.5, 2.8, ... (50 more values follow))], [REAL* (1.4, 1.4, 1.3, 1.5, 1.4, 1.7, 1.4, 1.5, 1.4, 1.5, 1.5, 1.6, 1.4, 1.1, 1.2, 1.5, 1.3, 1.4, 1.7, 1.5, 1.7, 1.5, 1.0, 1.7, 1.9, 1.6, 1.6, 1.5, 1.4, 1.6, 1.6, 1.5, 1.5, 1.4, 1.5, 1.2, 1.3, 1.4, 1.3, 1.5, 1.3, 1.3, 1.3, 1.6, 1.9, 1.4, 1.6, 1.4, 1.5, 1.4, 4.7, 4.5, 4.9, 4.0, 4.6, 4.5, 4.7, 3.3, 4.6, 3.9, 3.5, 4.2, 4.0, 4.7, 3.6, 4.4, 4.5, 4.1, 4.5, 3.9, 4.8, 4.0, 4.9, 4.7, 4.3, 4.4, 4.8, 5.0, 4.5, 3.5, 3.8, 3.7, 3.9, 5.1, 4.5, 4.5, 4.7, 4.4, 4.1, 4.0, 4.4, 4.6, 4.0, 3.3, 4.2, 4.2, 4.2, 4.3, 3.0, 4.1, ... (50 more values follow))], [REAL* (0.2, 0.2, 0.2, 0.2, 0.2, 0.4, 0.3, 0.2, 0.2, 0.1, 0.2, 0.2, 0.1, 0.1, 0.2, 0.4, 0.4, 0.3, 0.3, 0.3, 0.2, 0.4, 0.2, 0.5, 0.2, 0.2, 0.4, 0.2, 0.2, 0.2, 0.2, 0.4, 0.1, 0.2, 0.2, 0.2, 0.2, 0.1, 0.2, 0.2, 0.3, 0.3, 0.2, 0.6, 0.4, 0.3, 0.2, 0.2, 0.2, 0.2, 1.4, 1.5, 1.5, 1.3, 1.5, 1.3, 1.6, 1.0, 1.3, 1.4, 1.0, 1.5, 1.0, 1.4, 1.3, 1.4, 1.5, 1.0, 1.5, 1.1, 1.8, 1.3, 1.5, 1.2, 1.3, 1.4, 1.4, 1.7, 1.5, 1.0, 1.1, 1.0, 1.2, 1.6, 1.5, 1.6, 1.5, 1.3, 1.3, 1.3, 1.2, 1.4, 1.2, 1.0, 1.3, 1.2, 1.3, 1.3, 1.1, 1.3, ... (50 more values follow))], [FACTOR {levels=("setosa","versicolor","virginica"),ids=(0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2)}])]

has names:

Sepal.Length

Sepal.Width

Petal.Length

Petal.Width

Species

and once again from the list:

Sepal.Length

Sepal.Width

Petal.Length

Petal.Width

Species

[BOOLi* ]

F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F F T T T F T F T F T F F T T T F T F F T F T T T T T T T T T F F F F T F T T T F F F T F F F F F T F F T F T T T T F T T T T T T F F T T T T T T F T T T T T T T T T T T T T T T T T T T T F T T T T T T T

[BOOLi* ]

isTRUE? true

[LIST [REAL* (1.0)]:[SYMBOL a],([LIST [STRING "foo"]:[SYMBOL b],([LIST [INT* (1, 2, 3, 4, 5)]:[SYMBOL c],(null)])])]

Keys:

a

b

c

Contents:

[REAL* (1.0)]

[STRING "foo"]

[INT* (1, 2, 3, 4, 5)]

[REAL* (6.0)]

Parsing

Result = 59278824, running eval

Result = 66228464, building REXP

REXP result = [STRING "iris"]

Parsing

Result = 54717432, running eval

Result = 59554488, building REXP

REXP result = [VECTOR ([REAL* (5.1, 4.9, 4.7, 4.6, 5.0, 5.4, 4.6, 5.0, 4.4, 4.9, 5.4, 4.8, 4.8, 4.3, 5.8, 5.7, 5.4, 5.1, 5.7, 5.1, 5.4, 5.1, 4.6, 5.1, 4.8, 5.0, 5.0, 5.2, 5.2, 4.7, 4.8, 5.4, 5.2, 5.5, 4.9, 5.0, 5.5, 4.9, 4.4, 5.1, 5.0, 4.5, 4.4, 5.0, 5.1, 4.8, 5.1, 4.6, 5.3, 5.0, 7.0, 6.4, 6.9, 5.5, 6.5, 5.7, 6.3, 4.9, 6.6, 5.2, 5.0, 5.9, 6.0, 6.1, 5.6, 6.7, 5.6, 5.8, 6.2, 5.6, 5.9, 6.1, 6.3, 6.1, 6.4, 6.6, 6.8, 6.7, 6.0, 5.7, 5.5, 5.5, 5.8, 6.0, 5.4, 6.0, 6.7, 6.3, 5.6, 5.5, 5.5, 6.1, 5.8, 5.0, 5.6, 5.7, 5.7, 6.2, 5.1, 5.7, ... (50 more values follow))], [REAL* (3.5, 3.0, 3.2, 3.1, 3.6, 3.9, 3.4, 3.4, 2.9, 3.1, 3.7, 3.4, 3.0, 3.0, 4.0, 4.4, 3.9, 3.5, 3.8, 3.8, 3.4, 3.7, 3.6, 3.3, 3.4, 3.0, 3.4, 3.5, 3.4, 3.2, 3.1, 3.4, 4.1, 4.2, 3.1, 3.2, 3.5, 3.6, 3.0, 3.4, 3.5, 2.3, 3.2, 3.5, 3.8, 3.0, 3.8, 3.2, 3.7, 3.3, 3.2, 3.2, 3.1, 2.3, 2.8, 2.8, 3.3, 2.4, 2.9, 2.7, 2.0, 3.0, 2.2, 2.9, 2.9, 3.1, 3.0, 2.7, 2.2, 2.5, 3.2, 2.8, 2.5, 2.8, 2.9, 3.0, 2.8, 3.0, 2.9, 2.6, 2.4, 2.4, 2.7, 2.7, 3.0, 3.4, 3.1, 2.3, 3.0, 2.5, 2.6, 3.0, 2.6, 2.3, 2.7, 3.0, 2.9, 2.9, 2.5, 2.8, ... (50 more values follow))], [REAL* (1.4, 1.4, 1.3, 1.5, 1.4, 1.7, 1.4, 1.5, 1.4, 1.5, 1.5, 1.6, 1.4, 1.1, 1.2, 1.5, 1.3, 1.4, 1.7, 1.5, 1.7, 1.5, 1.0, 1.7, 1.9, 1.6, 1.6, 1.5, 1.4, 1.6, 1.6, 1.5, 1.5, 1.4, 1.5, 1.2, 1.3, 1.4, 1.3, 1.5, 1.3, 1.3, 1.3, 1.6, 1.9, 1.4, 1.6, 1.4, 1.5, 1.4, 4.7, 4.5, 4.9, 4.0, 4.6, 4.5, 4.7, 3.3, 4.6, 3.9, 3.5, 4.2, 4.0, 4.7, 3.6, 4.4, 4.5, 4.1, 4.5, 3.9, 4.8, 4.0, 4.9, 4.7, 4.3, 4.4, 4.8, 5.0, 4.5, 3.5, 3.8, 3.7, 3.9, 5.1, 4.5, 4.5, 4.7, 4.4, 4.1, 4.0, 4.4, 4.6, 4.0, 3.3, 4.2, 4.2, 4.2, 4.3, 3.0, 4.1, ... (50 more values follow))], [REAL* (0.2, 0.2, 0.2, 0.2, 0.2, 0.4, 0.3, 0.2, 0.2, 0.1, 0.2, 0.2, 0.1, 0.1, 0.2, 0.4, 0.4, 0.3, 0.3, 0.3, 0.2, 0.4, 0.2, 0.5, 0.2, 0.2, 0.4, 0.2, 0.2, 0.2, 0.2, 0.4, 0.1, 0.2, 0.2, 0.2, 0.2, 0.1, 0.2, 0.2, 0.3, 0.3, 0.2, 0.6, 0.4, 0.3, 0.2, 0.2, 0.2, 0.2, 1.4, 1.5, 1.5, 1.3, 1.5, 1.3, 1.6, 1.0, 1.3, 1.4, 1.0, 1.5, 1.0, 1.4, 1.3, 1.4, 1.5, 1.0, 1.5, 1.1, 1.8, 1.3, 1.5, 1.2, 1.3, 1.4, 1.4, 1.7, 1.5, 1.0, 1.1, 1.0, 1.2, 1.6, 1.5, 1.6, 1.5, 1.3, 1.3, 1.3, 1.2, 1.4, 1.2, 1.0, 1.3, 1.2, 1.3, 1.3, 1.1, 1.3, ... (50 more values follow))], [FACTOR {levels=("setosa","versicolor","virginica"),ids=(0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2)}])]

Parsing

Result = 54722488, running eval

Result = 59554264, building REXP

REXP result = [STRING* ("Sepal.Length", "Sepal.Width", "Petal.Length", "Petal.Width", "Species")]

[0] "Sepal.Length"

[1] "Sepal.Width"

[2] "Petal.Length"

[3] "Petal.Width"

[4] "Species"

Parsing

Result = 54722392, running eval

Result = 58316336, building REXP

REXP result = [REAL* (-0.18945291321042293, -1.849701024870639, -1.5554362607982648, 0.5990838636624077, -0.3034793177677859, -1.7781090129037724, 0.35644623327794134, -0.17655333079642885, -0.4089712138070159, -1.9775440799762682)]

-0.18945291321042293, -1.849701024870639, -1.5554362607982648, 0.5990838636624077, -0.3034793177677859, -1.7781090129037724, 0.35644623327794134, -0.17655333079642885, -0.4089712138070159, -1.9775440799762682

REXP result = [INT* (1, 2, 3, 4, 5, 6, 7, 8, 9, 10)]

1, 2, 3, 4, 5, 6, 7, 8, 9, 10

[1] 0.3333333 0.6666667 1.0000000 1.3333333 1.6666667 2.0000000 2.3333333

[8] 2.6666667 3.0000000 3.3333333

Now the console is yours ... have fun

rBusy(0)

> print("hello")

rBusy(1)

[1] "hello"

rBusy(0)

>

3.3     可能出现的错误

3.3.1  Cannot find JRI native library!

Press <Enter> to continue (time to attach the debugger if necessary)

Creating Rengine (with arguments)

Cannot find JRI native library!

Please make sure that the JRI native library is in a directory listed in java.library.path.

java.lang.UnsatisfiedLinkError: no jri in java.library.path

at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1860)

at java.lang.Runtime.loadLibrary0(Runtime.java:845)

at java.lang.System.loadLibrary(System.java:1084)

at org.rosuda.JRI.Rengine.<clinit>(Rengine.java:19)

at com.rTest.rtest2.main(rtest2.java:73)

检查下path是否正确，如果正确

重启下Eclipse 即可，如果不行，重启电脑。