maths.java

MacroWeka扩展了著名数据挖掘工具weka

/*
 * This software is a cooperative product of The MathWorks and the National
 * Institute of Standards and Technology (NIST) which has been released to the
 * public domain. Neither The MathWorks nor NIST assumes any responsibility
 * whatsoever for its use by other parties, and makes no guarantees, expressed
 * or implied, about its quality, reliability, or any other characteristic.
 */

/*
 * Maths.java
 * Copyright (C) 1999 The Mathworks and NIST
 *
 */

package weka.core.matrix;

/**
 * Utility class.
 * <p/>
 * Adapted from the <a href="http://math.nist.gov/javanumerics/jama/" target="_blank">JAMA</a> package.
 *
 * @author The Mathworks and NIST 
 * @author Fracpete (fracpete at waikato dot ac dot nz)
 * @version $Revision: 1.1 $
 */
 
public class Maths {

  /** 
   * sqrt(a^2 + b^2) without under/overflow. 
   */
  public static double hypot(double a, double b) {
    double r;
    if (Math.abs(a) > Math.abs(b)) {
      r = b/a;
      r = Math.abs(a)*Math.sqrt(1+r*r);
    } else if (b != 0) {
      r = a/b;
      r = Math.abs(b)*Math.sqrt(1+r*r);
    } else {
      r = 0.0;
    }
    return r;
  }
}