AlgoRSquare.java

/* 
GeoGebra - Dynamic Mathematics for Schools
Copyright Markus Hohenwarter and GeoGebra Inc.,  http://www.geogebra.org

This file is part of GeoGebra.

This program is free software; you can redistribute it and/or modify it 
under the terms of the GNU General Public License as published by 
the Free Software Foundation.

 */

package org.geogebra.common.kernel.statistics;

import org.geogebra.common.kernel.Construction;
import org.geogebra.common.kernel.algos.AlgoElement;
import org.geogebra.common.kernel.commands.Commands;
import org.geogebra.common.kernel.geos.GeoElement;
import org.geogebra.common.kernel.geos.GeoFunction;
import org.geogebra.common.kernel.geos.GeoFunctionable;
import org.geogebra.common.kernel.geos.GeoList;
import org.geogebra.common.kernel.geos.GeoNumeric;
import org.geogebra.common.kernel.geos.GeoPoint;

/**
 * Command: RSquare[<list>,<function>] Calculates coefficient of determination,
 * R^2, for a function f(x) fitted to the list.
 * 
 * @author G.Sturr
 */

public class AlgoRSquare extends AlgoElement {

	private GeoList inputList; // input
	private GeoFunctionable function; // input
	private GeoNumeric r2; // output
	private int size;

	public AlgoRSquare(Construction cons, String label, GeoList inputList,
			GeoFunctionable function) {
		this(cons, inputList, function);
		r2.setLabel(label);
	}

	public AlgoRSquare(Construction cons, GeoList inputList,
			GeoFunctionable function) {
		super(cons);
		this.inputList = inputList;
		this.function = function;

		r2 = new GeoNumeric(cons);

		setInputOutput();
		compute();
	}

	@Override
	public Commands getClassName() {
		return Commands.RSquare;
	}

	@Override
	protected void setInputOutput() {
		input = new GeoElement[2];
		input[0] = inputList;
		input[1] = function.toGeoElement();

		setOnlyOutput(r2);
		setDependencies(); // done by AlgoElement
	}

	public GeoNumeric getRSquare() {
		return r2;
	}

	@Override
	public final void compute() {

		size = inputList.size();
		if (!inputList.isDefined() || !function.toGeoElement().isDefined()) {
			r2.setUndefined();
			return;
		}

		GeoFunction funGeo = function.getGeoFunction();

		// Calculate errorsum and ssy:
		double sumyy = 0.0d;
		double sumy = 0.0d;
		double syy = 0.0d;
		double errorsum = 0.0d;
		GeoElement geo = null;
		GeoPoint point = null;
		double x, y, v;

		for (int i = 0; i < size; i++) {
			geo = inputList.get(i);
			if (geo instanceof GeoPoint) {
				point = (GeoPoint) geo;
				x = point.getX();
				y = point.getY();
				v = funGeo.value(x);
				errorsum += (v - y) * (v - y);
				sumy += y;
				sumyy += y * y;
			} else {
				r2.setUndefined();
				return;
			} // if calculation is possible
		} // for all points

		syy = sumyy - sumy * sumy / size;

		// calculate RSquare
		r2.setValue(1 - errorsum / syy);

	}// compute()

}// class AlgoRSquare