JRI and R - not able to capture output

Question

I am trying to plot some graphs using Java and R (JRI and Rengine). When I write something like this in my code it works fine:

re.eval("plot(c(1,5,3,8,5), type='l', col=2)");

But if I write this:

re.eval("source(\"C:\\Documents and Settings\\abc\\My Documents\\Test Data\\BoxPlot.r\");");

the output window flashes for a moment and vanishes. This specified file contains only 1 command, as the first one, i.e. re.eval("plot(c(1,5,3,8,5), type='l', col=2)");

I am very new to R, so this may be a very basic question. But I am not able to find it out. Can anyone help me out?

Thanks.

EDIT 1

I am using Windows XP.

Here is the full code:

import org.rosuda.JRI.Rengine;

public class JavaGDExample1 {

  public static void main(String[] args) {
    Rengine re;
    String[] dummyArgs = new String[1];
    dummyArgs[0] = "--vanilla";
    re = new Rengine(dummyArgs, false, null);
    re.eval("library(JavaGD)");

    // This is the critical line: Here, we tell R that the JavaGD() device that
    // it is supposed to draw to is implemented in the class MyJavaGD. If it were
    // in a package (say, my.package), this should be set to
    // my/package/MyJavaGD1.
    re.eval("Sys.putenv('JAVAGD_CLASS_NAME'='MyJavaGD1')");

    re.eval("JavaGD()");
//    re.eval("plot(c(1,5,3,8,5), type='l', col=2)");
    re.eval("source(\"C:\\Documents and Settings\\abc\\My Documents\\Test Data\\BoxPlot.r\");");
//    re.eval("source(\"C:\\Documents and Settings\\abc\\My Documents\\Test Data\\testPlot.r\")");
    re.end();
  }
}


import javax.swing.JFrame;

import org.rosuda.javaGD.GDCanvas;
import org.rosuda.javaGD.GDInterface;

/**
 * This is a minimal reimplementation of the GDInterface. When the device is opened, 
 * it just creates a new JFrame, adds a new GDCanvas to it (R will plot to this GDCanvas)
 * and tells the program to exit when it is closed.   
 */
public class MyJavaGD1 extends GDInterface {
  public JFrame f;

  public void gdOpen(double w, double h) {
    f = new JFrame("JavaGD");
    c = new GDCanvas(w, h);
    f.add((GDCanvas) c);
    f.pack();
    f.setVisible(true);
    f.setTitle("Naked R plot");
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  }

}

Answer 1

You path is wrong - you're entering the quoting hell, what you sent to R is

 source("C:\Documents and Settings\abc\My Documents\Test Data\BoxPlot.r");

which is invalid:

 > source("C:\Documents and Settings\abc\My Documents\Test Data\BoxPlot.r");
 Error: '\D' is an unrecognized escape in character string starting "C:\D"

To avoid the quoting hell, it is safer to assign file names:

 re.assign("fn", "c:\\foo\\bar");
 re.eval("source(fn)");

or use / instead of \\

PS: use stats-rosuda-devel for rJava/JRI questions

Answer 2

re.eval("Sys.putenv('JAVAGD_CLASS_NAME'='MyJavaGD1')");

should be now

re.eval("Sys.Sys.setenv('JAVAGD_CLASS_NAME'='MyJavaGD1')");

Sys.setenv() is a new (and preferred) synonym for Sys.putenv() and is now deprecated in favour of Sys.setenv().

source