calling R script from java

Question

I would like to call an R script from Java. I have done google searches on the topic, but almost all of the results I have seen would require me to add a dependency to some

Answer 1

...would require me to add a dependency to some third party library...

Why is that so bad? You make it sound like "...would require me to assault a honeybadger with a baseball bat..." I don't see the harm, especially if it works.

Maybe RCaller can help you. No JNI required.

Answer 2

BufferedReader reader = null;
        Process shell = null;
        try {
            shell = Runtime.getRuntime().exec(new String[] { "/usr/bin/Rscript", "/media/subin/works/subzworks/RLanguage/config/predict.R" });

            reader = new BufferedReader(new InputStreamReader(shell.getInputStream()));
            String line;
            while ((line = reader.readLine()) != null) {
                System.out.println(line);

            }

        } catch (IOException e) {
            e.printStackTrace();
        }

Answer 3

You can easily adapt this code: http://svn.rforge.net/org/trunk/rosuda/REngine/Rserve/test/StartRserve.java

Among other things it finds R and runs a fixed script in R - you can replace that script with with your script and ignore the last two methods.

Answer 4

Do not wait for the process to finish with Thread.sleep()...

Use the waitFor() method instead.

Process child = Runtime.getRuntime().exec(command, environments, dataDir);

int code = child.waitFor();

switch (code) {
    case 0:
        //normal termination, everything is fine
        break;
    case 1:
        //Read the error stream then
        String message = IOUtils.toString(child.getErrorStream());
        throw new RExecutionException(message);
}

Answer 5

You just want to call an external application: wouldn't the following work?

Runtime.getRuntime().exec("Rscript myScript.R");