Is there a way to use R in a java applet?

Question

I want to create a java applet that takes various files and runs statistical tests on them. The user would choose a file and press the appropriate button for a statistical test. All of the statistical tests would be coded in R. Is there a way to "bridge" R and Java?

Answer 1

The kind of functionality you are looking for is readily available in R itself. The Shiny package, created by RStudio, does exactly what you need: provide a web interface to R including simple GUI elements. The advantage of using Shiny is that it takes care of all the nitty gritty details, letting you focus on the analyses. It literally took me 2 hours to install Shiny and create my first web app.

Disclaimer: I do not have any affiliations with RStudio, I'm just a happy user :).

Answer 2

Is there a way to "bridge" R and Java?

There certainly is. You can use JRI.

Here is a JRI Java to R example that I provided in a previous answer (passing a double array and having R sum it):

// Start R session.
Rengine re = new Rengine (new String [] {"--vanilla"}, false, null);

// Check if the session is working.
if (!re.waitForR()) {
  return;
}

re.assign("x", new double[] {1.5, 2.5, 3.5});
REXP result = re.eval("(sum(x))");
System.out.println(result.asDouble());
re.end();

The above is basically the equivalent of doing this in R:

x <- c(1.5, 2.5, 3.5)
sum(x)

Note: If you're using Eclipse and JRI I highly recommend this plugin to set it up.

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Alternatively you just create R scripts that you execute from Java using RScript.exe. For example:

Rscript my_script.R

You will find plenty of information on the internet explaining how to execute command line commands from Java. I don't know enough about it to give you an example.