R from within Java

Question

What's the best way to call R functionality from within Java?

I'm looking for a quick, easy and reliable way to make standard 2d scatter plots and histograms in R using my Java applications. I was wondering which packages/interfaces that came up in a quick Google search would be most convenient to use.

I look forward to your suggestions!

Answer 1

Use JRI: http://www.rforge.net/JRI/. It comes bundled with rJava, including some examples of usage.

A very simple example would be like this:

import java.io.*;
import java.awt.Frame;
import java.util.Enumeration;

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

public class rJavaTest {

    public static void main(String[] args) {

        Rengine re=new Rengine(args, false, new TextConsole());
        REXP x;
        re.eval("print(1:10/3)");
        System.out.println(x=re.eval("iris"));
        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());
            }
        }

        if (true) {
            System.out.println("Now the console is yours ... have fun");
            re.startMainLoop();
        } else {
            re.end();
            System.out.println("end");
        }
    }
}

Answer 2

I have found that forking R as a process, attaching to the process's stdin, stdout, and stderr streams, and sending R commands via the input stream to be quite effective. I use the filesystem to communicate between R and my Java process. This way, I can have multiple R processes running from different threads in Java and their environments do not conflict with each other.

Answer 3

Thanks for the example !!! Do you Know how can i use it whith an applet ?? i`m working whith Eclipses.

Thankssssssssssss !!!