curve fitting

RSample.java

package rJava;

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

public class RSample {
	public static void main(String[] args) {
		System.out.println("R_HOME:" + System.getenv("R_HOME"));
		System.out.println("java.library.path:"
				+ System.getProperty("java.library.path"));

		Rengine engine = new Rengine(new String[] {
			"--no-save"
		}, false, null);

		try {
			String filename = "dist.dat";
			engine.eval("data<-read.csv(\"" + filename + "\")");
			engine.eval("x<-data[,1]");
			engine.eval("y<-data[,2]");

			String[] exprs = {
					"a*x+b", "a*x^b", "a*b^x"
			};
			for (String expr : exprs) {
				double[] r = func(engine, expr);
				String out = expr;
				out += (": a=" + r[0]);
				out += (", b=" + r[1]);
				out += ("  (AIC " + r[2] + ")");
				System.out.println(out);
			}
		} finally {
			engine.end();
		}
	}

	private static double[] func(Rengine engine, String f) {
		engine.eval("result<-nls(y~(" + f + "), start=c(a=1, b=1))");
		REXP result0 = engine.eval("summary(result)");
		REXP result1 = engine.eval("AIC(result)");
		double[] c = ((result0.asVector()).at("parameters")).asDoubleArray();
		double[] ret = {
				c[0], c[1], result1.asDouble()
		};
		return ret;
	}
}