JAVA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。

Rserve方式

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。

客户端，下载REngine.jar和RserveEngine.jar两个文件。

启动"Rserve"

import org.rosuda.REngine.REXP;
import org.rosuda.REngine.Rserve.RConnection;

public class RserveHandler {

	/**
	 * Application entry point.
	 */
	public static void main(String[] args) {
		try {
			RConnection conn = new RConnection();
			REXP ex = conn.eval("R.version.string");
			System.out.println(ex.asString());
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

JRI方式　　

Java/R Interface，通过调用R的动态链接库从而利用R中的函数。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。

配置环境变量：

  PATH  .;%JAVA_HOME%\bin;%M2_HOME%\bin;%R_HOME%\bin\x64;%R_HOME%\library\rJava\jri\x64

package com.nsecn.rns;

import java.awt.FileDialog;
import java.awt.Frame;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Enumeration;

import org.rosuda.JRI.REXP;
import org.rosuda.JRI.RList;
import org.rosuda.JRI.RMainLoopCallbacks;
import org.rosuda.JRI.RVector;
import org.rosuda.JRI.Rengine;

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 + "\"");
    }

    @SuppressWarnings("deprecation")
    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 JIRunit {

    /**
     * Application entry point.
     */
    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)");

        boolean flag = true;
        if (flag) {
            // 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.nsecn.rns;

import java.awt.Dimension;
import java.awt.FileDialog;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintStream;

import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;

import org.rosuda.JRI.RConsoleOutputStream;
import org.rosuda.JRI.RMainLoopCallbacks;
import org.rosuda.JRI.Rengine;

class TextConsole2 implements RMainLoopCallbacks {

    JFrame frame;

    public JTextArea textarea = new JTextArea();

    @SuppressWarnings("deprecation")
    public TextConsole2() {
        frame = new JFrame();
        frame.getContentPane().add(new JScrollPane(textarea));
        frame.setSize(new Dimension(800, 600));
        frame.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 + "\"");
    }

    @SuppressWarnings("deprecation")
    public String rChooseFile(Rengine re, int newFile) {
        FileDialog fd = new FileDialog(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 JRIano {

    /**
     * Application entry point.
     */
    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");
    }
}