Java-R: R bridge "JRI" error already initialized

Question

I use JRI as a calculation sheet for statistics from Java. R-calculations are required from time to time, but not too often. So I decided to create a wrapper method for computation that creates a new instance of REngine and also closes it to the end. When you first call the method, everything works like a charm. Unfortunately, calling it a second time causes the error "R is already initialized."

Initialization:

private static Rengine createEngineInstance(){ //Initialise R Engine. Rengine re=new Rengine (new String [] {"--vanilla"}, false, new CallbackListener()); //Wait until REngine-thread is ready if (!re.waitForR()) { System.err.println ("Cannot load R. Is the environment variable R_HOME set correctly?"); System.exit(1); } return re; } 

Wrap Method:

 public static void performR(){ //Create instance of R engine Rengine re = createEngineInstance(); //Perform some R operations re.eval("..."); re.end(); } 

Obviously, the REngine instance is not completed correctly. So I need to know: 1) Is it possible to stop REngine and create a new instance later? How does it work correctly? I know that it is not possible to run multiple R threads at the same time as the JRI, but that is not what I am aiming for. 2) If this is not the case, I would create one instance using the Singleton template. How can I ensure in this case that the R session closes when the program terminates?

Your help is much appreciated! Thanks!

Answer 1

according to JRI Javadoc ....

Only one instance of Rengine can be used, and the Rengine.end () function has some problems ...

you should not use such code

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

you can use rengine with this code

 Rengine engine = Rengine.getMainEngine(); if(engine == null) engine = new Rengine(new String[] {"--vanilla"}, false, null); 

Answer 2

A very old question, but I would add that considering RServe as an alternative is often attractive. The setup is less involved (in my opinion), and the interface is almost identical.

Detailed tutorial given here .

This has the added benefit that if you ever want to make R calls from parallel Java threads, you can do it.