Adding in regression to the library

src/main/java/com/robototes/math/Equation.java

@@ -0,0 +1,67 @@
+package com.robototes.math;
+
+/**
+ * 
+ * @author OroArmor
+ *
+ */
+public class Equation {
+	private double[] terms;
+
+	/**
+	 * 
+	 * @param terms the terms for the equation, currently only doubles are
+	 *              supported. terms go from x^0 to x^n.
+	 */
+	public Equation(double... terms) {
+		this.terms = terms;
+	}
+
+	public double calculate(double x) {
+
+		double t = 1;
+		double y = 0;
+
+		for (double term : terms) {
+			y += term * t;
+			t *= x;
+		}
+
+		return y;
+	}
+
+	public double[] getTerms() {
+		return terms;
+	}
+
+	@Override
+	public String toString() {
+		String equation = "";
+		int i = 0;
+		for (double term : terms) {
+			equation = term + ((i++ != 0) ? "x^" + (i - 1) + " + " : "") + equation;
+		}
+
+		return "y = " + equation;
+	}
+
+	@Override
+	public boolean equals(Object o) {
+		if (!(o instanceof Equation)) {
+			return false;
+		} else {
+			Equation other = (Equation) o;
+
+			if (other.terms.length != this.terms.length) {
+				return false;
+			}
+
+			for (int i = 0; i < this.terms.length; i++) {
+				if (!MathUtils.epsilonEquals(this.terms[i], other.terms[i], MathUtils.EPSILON)) {
+					return false;
+				}
+			}
+		}
+		return true;
+	}
+}

src/main/java/com/robototes/math/SimpleRegression.java

@@ -0,0 +1,48 @@
+package com.robototes.math;
+
+public class SimpleRegression {
+
+	/**
+	 * 
+	 * @param pointOne
+	 * @param pointTwo
+	 * @return An equation that goes through all points
+	 */
+	public static Equation linearRegression(Vector pointOne, Vector pointTwo) {
+
+		double m = (pointTwo.y - pointOne.y) / (pointTwo.x - pointOne.x);
+
+		double b = pointTwo.y - m * pointTwo.x;
+
+		return new Equation(b, m);
+	}
+
+	/**
+	 * 
+	 * @param pointOne
+	 * @param pointTwo
+	 * @param pointThree
+	 * @return An quadratic equation that goes through the three points.
+	 */
+	public static Equation quadraticRegression(Vector pointOne, Vector pointTwo, Vector pointThree) {
+		// Lagrange polynomial
+		double bottom1 = (pointOne.x * pointOne.x - (pointTwo.x + pointThree.x) * pointOne.x
+				+ pointTwo.x * pointThree.x);
+		double bottom2 = (pointTwo.x * pointTwo.x - (pointOne.x + pointThree.x) * pointTwo.x
+				+ pointOne.x * pointThree.x);
+		double bottom3 = (pointThree.x * pointThree.x - (pointOne.x + pointTwo.x) * pointThree.x
+				+ pointOne.x * pointTwo.x);
+
+		double coeff1 = pointOne.y / bottom1;
+		double coeff2 = pointTwo.y / bottom2;
+		double coeff3 = pointThree.y / bottom3;
+
+		double a = +(coeff1 + coeff2 + coeff3);
+		double b = -((pointTwo.x + pointThree.x) * coeff1 + (pointOne.x + pointThree.x) * coeff2
+				+ (pointOne.x + pointTwo.x) * coeff3);
+		double c = +((pointTwo.x * pointThree.x) * coeff1 + (pointOne.x * pointThree.x) * coeff2
+				+ (pointOne.x * pointTwo.x) * coeff3);
+
+		return new Equation(c, b, a);
+	}
+}

src/test/java/com/robototes/math/DoubleRatioTest.java

@@ -11,16 +11,15 @@ public void testCalculateRatio() {
 		DoubleRatio one = new DoubleRatio(10, "a", "b");
 
 		assertEquals("Calculate double ratio", one.calculateRatio(10), 100, MathUtils.EPSILON);
-		assertEquals("Calculate Double ratio", one.calculateRatio(new Double(0.1)), 1, MathUtils.EPSILON);
+		assertEquals("Calculate Double ratio", one.calculateRatio(0.1), 1, MathUtils.EPSILON);
 	}
 
 	@Test
 	public void testCalculateReverseRatio() {
 		DoubleRatio one = new DoubleRatio(10, "a", "b");
 
 		assertEquals("Calculate reverse double ratio", one.calculateReverseRatio(10), 1, MathUtils.EPSILON);
-		assertEquals("Calculate reverse Double ratio", one.calculateReverseRatio(new Double(1)), 0.1,
-				MathUtils.EPSILON);
+		assertEquals("Calculate reverse Double ratio", one.calculateReverseRatio(1), 0.1, MathUtils.EPSILON);
 	}
 
 	@Test

src/test/java/com/robototes/math/EquationTest.java

@@ -0,0 +1,15 @@
+package com.robototes.math;
+
+import static org.junit.Assert.*;
+
+import org.junit.Test;
+
+public class EquationTest {
+
+	@Test
+	public void testCalculate() {
+		Equation equation = new Equation(0, 0, 1); // y = x^2
+		double x = 3;
+		assertEquals("Simple equation has correct value", x * x, equation.calculate(x), MathUtils.EPSILON);
+	}
+}

src/test/java/com/robototes/math/SimpleRegressionTest.java

@@ -0,0 +1,26 @@
+package com.robototes.math;
+
+import static org.junit.Assert.*;
+
+import org.junit.Test;
+
+public class SimpleRegressionTest {
+
+	@Test
+	public void testLinearRegression() {
+		Vector a = new Vector(0, 0);
+		Vector b = new Vector(1, 1);
+
+		assertEquals("Linear Regression", new Equation(0, 1), SimpleRegression.linearRegression(a, b));
+	}
+
+	@Test
+	public void testQuadraticRegression() {
+		Vector a = new Vector(0, 0);
+		Vector b = new Vector(1, 1);
+		Vector c = new Vector(2, 4);
+
+		assertEquals("Quadratic Regression", new Equation(0, 0, 1), SimpleRegression.quadraticRegression(a, b, c));
+	}
+
+}