source: trunk/gsdl/packages/kea/kea-3.0/weka/core/Utils.java@ 8815

/*
 *    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; either version 2 of the License, or
 *    (at your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/*
 *    Utils.java
 *    Copyright (C) 1999 Eibe Frank,Len Trigg,Yong Wang
 *
 */

package weka.core;

import java.lang.Math;
import java.util.StringTokenizer;
import java.util.Properties;
import java.io.File;
import java.io.FileInputStream;

/**
 * Class implementing some simple utility methods.
 *
 * @author Eibe Frank ([email protected])
 * @author Yong Wang ([email protected])
 * @author Len Trigg ([email protected])
 * @version $Revision: 8815 $
 */
public final class Utils {

  /** The natural logarithm of 2. */
  public static double log2 = Math.log(2);

  /** The small deviation allowed in double comparisons */
  public static double SMALL = 1e-6;

  
  /**
   * Reads properties that inherit from three locations. Properties
   * are first defined in the system resource location (i.e. in the
   * CLASSPATH).  These default properties must exist. Properties
   * defined in the users home directory (optional) override default
   * settings. Properties defined in the current directory (optional)
   * override all these settings.
   *
   * @param resourceName the location of the resource that should be
   * loaded.  e.g.: "weka/core/Utils.props". (The use of hardcoded
   * forward slashes here is OK - see
   * jdk1.1/docs/guide/misc/resources.html) This routine will also
   * look for the file (in this case) "Utils.props" in the users home
   * directory and the current directory.
   * @return the Properties
   * @exception Exception if no default properties are defined, or if
   * an error occurs reading the properties files.  
   */
  public static Properties readProperties(String resourceName)
    throws Exception{

    Properties defaultProps = new Properties();
    try {
      // Apparently hardcoded slashes are OK here
      // jdk1.1/docs/guide/misc/resources.html
      defaultProps.load(ClassLoader.getSystemResourceAsStream(resourceName));
    } catch (Exception ex) {
/*      throw new Exception("Problem reading default properties: "
    + ex.getMessage()); */
      System.err.println("Warning, unable to load properties file from "
             +"system resource (Utils.java)");
    }

    // Hardcoded slash is OK here
    // eg: see jdk1.1/docs/guide/misc/resources.html
    int slInd = resourceName.lastIndexOf('/');
    if (slInd != -1) {
      resourceName = resourceName.substring(slInd + 1);
    }

    // Allow a properties file in the home directory to override
    Properties userProps = new Properties(defaultProps);    
    File propFile = new File(System.getProperties().getProperty("user.home")
                             + File.separatorChar
                             + resourceName);
    if (propFile.exists()) {
      try {
        userProps.load(new FileInputStream(propFile));
      } catch (Exception ex) {
        throw new Exception("Problem reading user properties: " + propFile);
      }
    }

    // Allow a properties file in the current directory to override
    Properties localProps = new Properties(userProps);
    propFile = new File(resourceName);
    if (propFile.exists()) {
      try {
        localProps.load(new FileInputStream(propFile));
      } catch (Exception ex) {
        throw new Exception("Problem reading local properties: " + propFile);
      }
    }
    
    return localProps;
  }

  /**
   * Returns the correlation coefficient of two double vectors.
   *
   * @param y1 double vector 1
   * @param y2 double vector 2
   * @param n the length of two double vectors
   * @return the correlation coefficient
   */
  public final static double correlation(double y1[],double y2[],int n) {

    int i;
    double av1 = 0.0, av2 = 0.0, y11 = 0.0, y22 = 0.0, y12 = 0.0, c;
    
    if (n <= 1) {
      return 1.0;
    }
    for (i = 0; i < n; i++) {
      av1 += y1[i];
      av2 += y2[i];
    }
    av1 /= (double) n;
    av2 /= (double) n;
    for (i = 0; i < n; i++) {
      y11 += (y1[i] - av1) * (y1[i] - av1);
      y22 += (y2[i] - av2) * (y2[i] - av2);
      y12 += (y1[i] - av1) * (y2[i] - av2);
    }
    if (y11 * y22 == 0.0) {
      c=1.0;
    } else {
      c = y12 / Math.sqrt(Math.abs(y11 * y22));
    }
    
    return c;
  }

  /**
   * Removes all occurrences of a string from another string.
   *
   * @param inString the string to remove substrings from.
   * @param substring the substring to remove.
   * @return the input string with occurrences of substring removed.
   */
  public static String removeSubstring(String inString, String substring) {

    StringBuffer result = new StringBuffer();
    int oldLoc = 0, loc = 0;
    while ((loc = inString.indexOf(substring, oldLoc))!= -1) {
      result.append(inString.substring(oldLoc, loc));
      oldLoc = loc + substring.length();
    }
    result.append(inString.substring(oldLoc));
    return result.toString();
  }

  /**
   * Replaces with a new string, all occurrences of a string from 
   * another string.
   *
   * @param inString the string to replace substrings in.
   * @param substring the substring to replace.
   * @param replaceString the replacement substring
   * @return the input string with occurrences of substring replaced.
   */
  public static String replaceSubstring(String inString, String subString,
                    String replaceString) {

    StringBuffer result = new StringBuffer();
    int oldLoc = 0, loc = 0;
    while ((loc = inString.indexOf(subString, oldLoc))!= -1) {
      result.append(inString.substring(oldLoc, loc));
      result.append(replaceString);
      oldLoc = loc + subString.length();
    }
    result.append(inString.substring(oldLoc));
    return result.toString();
  }


  /**
   * Pads a string to a specified length, inserting spaces on the left
   * as required. If the string is too long, characters are removed (from
   * the right).
   *
   * @param inString the input string
   * @param length the desired length of the output string
   * @return the output string
   */
  public static String padLeft(String inString, int length) {

    return fixStringLength(inString, length, false);
  }
  
  /**
   * Pads a string to a specified length, inserting spaces on the right
   * as required. If the string is too long, characters are removed (from
   * the right).
   *
   * @param inString the input string
   * @param length the desired length of the output string
   * @return the output string
   */
  public static String padRight(String inString, int length) {

    return fixStringLength(inString, length, true);
  }
  
  /**
   * Pads a string to a specified length, inserting spaces as
   * required. If the string is too long, characters are removed (from
   * the right).
   *
   * @param inString the input string
   * @param length the desired length of the output string
   * @param right true if inserted spaces should be added to the right
   * @return the output string
   */
  private static String fixStringLength(String inString, int length,
                    boolean right) {

    if (inString.length() < length) {
      while (inString.length() < length) {
    inString = (right ? inString.concat(" ") : " ".concat(inString));
      }
    } else if (inString.length() > length) {
      inString = inString.substring(0, length);
    }
    return inString;
  }
 
  /**
   * Rounds a double and converts it into String.
   *
   * @param value the double value
   * @param afterDecimalPoint the (maximum) number of digits permitted
   * after the decimal point
   * @return the double as a formatted string
   */
  public static String doubleToString(double value, int afterDecimalPoint) {
    
    StringBuffer stringBuffer;
    double temp;
    int i,dotPosition;
    long precisionValue;
    
    temp = value * Math.pow(10.0, afterDecimalPoint);
    if (Math.abs(temp) < Long.MAX_VALUE) {
      precisionValue =  (temp > 0) ? (long)(temp + 0.5) 
                                   : -(long)(Math.abs(temp) + 0.5);
      if (precisionValue == 0) {
    stringBuffer = new StringBuffer(String.valueOf(0));
      } else {
    stringBuffer = new StringBuffer(String.valueOf(precisionValue));
      }
      if (afterDecimalPoint == 0) {
    return stringBuffer.toString();
      }
      dotPosition = stringBuffer.length() - afterDecimalPoint;
      while (((precisionValue < 0) && (dotPosition < 1)) ||
         (dotPosition < 0)) {
    if (precisionValue < 0) {
      stringBuffer.insert(1, 0);
    } else {
      stringBuffer.insert(0, 0);
    }
    dotPosition++;
      }
      stringBuffer.insert(dotPosition, '.');
      if ((precisionValue < 0) && (stringBuffer.charAt(1) == '.')) {
    stringBuffer.insert(1, 0);
      } else if (stringBuffer.charAt(0) == '.') {
    stringBuffer.insert(0, 0);
      }
      int currentPos = stringBuffer.length() - 1;
      while ((currentPos > dotPosition) &&
         (stringBuffer.charAt(currentPos) == '0')) {
    stringBuffer.setCharAt(currentPos--, ' ');
      }
      if (stringBuffer.charAt(currentPos) == '.') {
    stringBuffer.setCharAt(currentPos, ' ');
      }
      
      return stringBuffer.toString().trim();
    }
    return new String("" + value);
  }

  /**
   * Rounds a double and converts it into a formatted decimal-justified String.
   * Trailing 0's are replaced with spaces.
   *
   * @param value the double value
   * @param width the width of the string
   * @param afterDecimalPoint the number of digits after the decimal point
   * @return the double as a formatted string
   */
  public static String doubleToString(double value, int width,
                      int afterDecimalPoint) {
    
    String tempString = doubleToString(value, afterDecimalPoint);
    char[] result;
    int dotPosition;

    if ((afterDecimalPoint >= width) 
        || (tempString.indexOf('E') != -1)) { // Protects sci notation
      return tempString;
    }

    // Initialize result
    result = new char[width];
    for (int i = 0; i < result.length; i++) {
      result[i] = ' ';
    }

    if (afterDecimalPoint > 0) {
      // Get position of decimal point and insert decimal point
      dotPosition = tempString.indexOf('.');
      if (dotPosition == -1) {
    dotPosition = tempString.length();
      } else {
    result[width - afterDecimalPoint - 1] = '.';
      }
    } else {
      dotPosition = tempString.length();
    }
    

    int offset = width - afterDecimalPoint - dotPosition;
    if (afterDecimalPoint > 0) {
      offset--;
    }

    // Not enough room to decimal align within the supplied width
    if (offset < 0) {
      return tempString;
    }

    // Copy characters before decimal point
    for (int i = 0; i < dotPosition; i++) {
      result[offset + i] = tempString.charAt(i);
    }

    // Copy characters after decimal point
    for (int i = dotPosition + 1; i < tempString.length(); i++) {
      result[offset + i] = tempString.charAt(i);
    }

    return new String(result);
  }

  /**
   * Tests if a is equal to b.
   *
   * @param a a double
   * @param b a double
   */
  public static boolean eq(double a, double b){
    
    return (a - b < SMALL) && (b - a < SMALL); 
  }

  /**
   * Checks if the given array contains any non-empty options.
   *
   * @param strings an array of strings
   * @exception Exception if there are any non-empty options
   */
  public static void checkForRemainingOptions(String [] options) 
    throws Exception {
    
    int illegalOptionsFound = 0;
    StringBuffer text = new StringBuffer();

    if (options == null) {
      return;
    }
    for (int i = 0; i < options.length; i++) {
      if (options[i].length() > 0) {
    illegalOptionsFound++;
    text.append(options[i] + ' ');
      }
    }
    if (illegalOptionsFound > 0) {
      throw new Exception("Illegal options: " + text);
    }
  }
  
  /**
   * Checks if the given array contains the flag "-Char". Stops
   * searching at the first marker "--". If the flag is found,
   * it is replaced with the empty string.
   *
   * @param flag the character indicating the flag.
   * @param strings the array of strings containing all the options.
   * @return true if the flag was found
   * @exception Exception if an illegal option was found
   */

  public static boolean getFlag(char flag, String [] options) 
    throws Exception {

    if (options == null) {
      return false;
    }
    for (int i = 0; i < options.length; i++) {
      if ((options[i].length() > 1) && (options[i].charAt(0) == '-')) {
    try {
      Double dummy = Double.valueOf(options[i]);
    } catch (NumberFormatException e) {
      if (options[i].length() > 2) {
        throw new Exception("Illegal option: " + options[i]);
      }
      if (options[i].charAt(1) == flag) {
        options[i] = "";
        return true;
      }
      if (options[i].charAt(1) == '-') {
        return false;
      }
    }
      }
    }
    return false;
  }

  /**
   * Gets an option indicated by a flag "-Char" from the given array
   * of strings. Stops searching at the first marker "--". Replaces 
   * flag and option with empty strings.
   *
   * @param flag the character indicating the option.
   * @param options the array of strings containing all the options.
   * @return the indicated option or an empty string
   * @exception Exception if the option indicated by the flag can't be found
   */
  public static String getOption(char flag, String [] options) 
    throws Exception {

    String newString;

    if (options == null)
      return "";
    for (int i = 0; i < options.length; i++) {
      if ((options[i].length() > 0) && (options[i].charAt(0) == '-')) {
    
    // Check if it is a negative number
    try {
      Double dummy = Double.valueOf(options[i]);
    } catch (NumberFormatException e) {
      if (options[i].length() > 2) {
        throw new Exception("Illegal option: " + options[i]);
      }
      if (options[i].charAt(1) == flag) {
        if (i + 1 == options.length) {
          throw new Exception("No value given for -" + flag + " option.");
        }
        options[i] = "";
        newString = new String(options[i + 1]);
        options[i + 1] = "";
        return newString;
      }
      if (options[i].charAt(1) == '-') {
        return "";
      }
    }
      }
    }
    return "";
  }

  /**
   * Quotes a string if it contains special characters.
   * 
   * The following rules are applied:
   *
   * A character is backquoted version of it is one 
   * of <tt>" ' % \ \n \r \t</tt>.
   *
   * A string is enclosed within single quotes if a character has been
   * backquoted using the previous rule above or contains 
   * <tt>{ }</tt> or is exactly equal to the strings 
   * <tt>, ? space or ""</tt> (empty string).
   *
   * A quoted question mark distinguishes it from the missing value which
   * is represented as an unquoted question mark in arff files.
   *
   * @param string the string to be quoted
   * @return the string (possibly quoted)
   */
  public static String quote(String string) {
      boolean quote = false;

      // backquote the following characters 
      if ((string.indexOf('\n') != -1) || (string.indexOf('\r') != -1) || 
      (string.indexOf('\'') != -1) || (string.indexOf('"') != -1) || 
      (string.indexOf('\\') != -1) || 
      (string.indexOf('\t') != -1) || (string.indexOf('%') != -1)) {
      string = backQuoteChars(string);
      quote = true;
      }

      // Enclose the string in 's if the string contains a recently added
      // backquote or contains one of the following characters.
      if((quote == true) || 
     (string.indexOf('{') != -1) || (string.indexOf('}') != -1) ||
     (string.indexOf(',') != -1) || (string.equals("?")) ||
     (string.indexOf(' ') != -1) || (string.equals(""))) {
      string = ("'".concat(string)).concat("'");
      }

      return string;
  }

  /**
   * Converts carriage returns and new lines in a string into \r and \n.
   * Backquotes the following characters: ` " \ \t and %
   * @param string the string
   * @return the converted string
   */
  public static String backQuoteChars(String string) {

    int index;
    StringBuffer newStringBuffer;

    // replace each of the following characters with the backquoted version
    char   charsFind[] =    {'\\',   '\'',  '\t',  '"',    '%'};
    String charsReplace[] = {"\\\\", "\\'", "\\t", "\\\"", "\\%"};
    for(int i = 0; i < charsFind.length; i++) {
    if (string.indexOf(charsFind[i]) != -1 ) {
        newStringBuffer = new StringBuffer();
        while ((index = string.indexOf(charsFind[i])) != -1) {
        if (index > 0) {
            newStringBuffer.append(string.substring(0, index));
        }
        newStringBuffer.append(charsReplace[i]);
        if ((index + 1) < string.length()) {
            string = string.substring(index + 1);
        } else {
            string = "";
        }
        }
        newStringBuffer.append(string);
        string = newStringBuffer.toString();
    }
    }

    return Utils.convertNewLines(string);
  }

  /**
   * Converts carriage returns and new lines in a string into \r and \n.
   * @param string the string
   * @return the converted string
   */
  public static String convertNewLines(String string) {
    
    int index;

    // Replace with \n
    StringBuffer newStringBuffer = new StringBuffer();
    while ((index = string.indexOf('\n')) != -1) {
      if (index > 0) {
    newStringBuffer.append(string.substring(0, index));
      }
      newStringBuffer.append('\\');
      newStringBuffer.append('n');
      if ((index + 1) < string.length()) {
    string = string.substring(index + 1);
      } else {
    string = "";
      }
    }
    newStringBuffer.append(string);
    string = newStringBuffer.toString();

    // Replace with \r
    newStringBuffer = new StringBuffer();
    while ((index = string.indexOf('\r')) != -1) {
      if (index > 0) {
    newStringBuffer.append(string.substring(0, index));
      }
      newStringBuffer.append('\\');
      newStringBuffer.append('r');
      if ((index + 1) < string.length()){
    string = string.substring(index + 1);
      } else {
    string = "";
      }
    }
    newStringBuffer.append(string);
    return newStringBuffer.toString();
  }
    

  /**
   * Returns the secondary set of options (if any) contained in
   * the supplied options array. The secondary set is defined to
   * be any options after the first "--". These options are removed from
   * the original options array.
   *
   * @param options the input array of options
   * @return the array of secondary options
   */
  public static String [] partitionOptions(String [] options) {

    for (int i = 0; i < options.length; i++) {
      if (options[i].equals("--")) {
    options[i++] = "";
    String [] result = new String [options.length - i];
    for (int j = i; j < options.length; j++) {
      result[j - i] = options[j];
      options[j] = "";
    }
    return result;
      }
    }
    return new String [0];
  }

  /**
   * Split up a string containing options into an array of strings,
   * one for each option.
   *
   * @param optionString the string containing the options
   * @return the array of options
   */
  public static String [] splitOptions(String optionString) {

    FastVector optionsVec = new FastVector();
    StringTokenizer st = new StringTokenizer(optionString);
    while (st.hasMoreTokens())
      optionsVec.addElement(st.nextToken());

    String [] options = new String[optionsVec.size()];
    for (int i = 0; i < optionsVec.size(); i++) {
      options[i] = (String)optionsVec.elementAt(i);
    }
    return options;
  }

  /**
   * Joins all the options in an option array into a single string,
   * as might be used on the command line.
   *
   * @param optionArray the array of options
   * @return the string containing all options.
   */
  public static String joinOptions(String [] optionArray) {

    String optionString = "";
    for (int i = 0; i < optionArray.length; i++) {
      if (optionArray[i].equals("")) {
    continue;
      }
      if (optionArray[i].indexOf(' ') != -1) {
    optionString += '"' + optionArray[i] + '"';
      } else {
    optionString += optionArray[i];
      }
      optionString += " ";
    }
    return optionString.trim();
  }
  
  /**
   * Creates a new instance of an object given it's class name and
   * (optional) arguments to pass to it's setOptions method. If the
   * object implements OptionHandler and the options parameter is
   * non-null, the object will have it's options set. Example use:<p>
   *
   * <code> <pre>
   * String classifierName = Utils.getOption('W', options);
   * Classifier c = (Classifier)Utils.forName(Classifier.class,
   *                                          classifierName,
   *                                          options);
   * setClassifier(c);
   * </pre></code>
   *
   * @param classType the class that the instantiated object should
   * be assignable to -- an exception is thrown if this is not the case
   * @param className the fully qualified class name of the object
   * @param options an array of options suitable for passing to setOptions. May
   * be null. Any options accepted by the object will be removed from the
   * array.
   * @return the newly created object, ready for use.
   * @exception Exception if the class name is invalid, or if the
   * class is not assignable to the desired class type, or the options
   * supplied are not acceptable to the object
   */
  public static Object forName(Class classType,
                   String className,
                   String [] options) throws Exception {

    Class c = null;
    try {
      c = Class.forName(className);
    } catch (Exception ex) {
      throw new Exception("Can't find class called: " + className);
    }
    if (!classType.isAssignableFrom(c)) {
      throw new Exception(classType.getName() + " is not assignable from "
              + className);
    }
    Object o = c.newInstance();
    if ((o instanceof OptionHandler)
    && (options != null)) {
      ((OptionHandler)o).setOptions(options);
      Utils.checkForRemainingOptions(options);
    }
    return o;
  }

  /**
   * Computes entropy for an array of integers.
   *
   * @param counts array of counts
   * @returns - a log2 a - b log2 b - c log2 c + (a+b+c) log2 (a+b+c)
   * when given array [a b c]
   */
  public static double info(int counts[]) {
    
    int total = 0; int c;
    double x = 0;
    for (int j = 0; j < counts.length; j++) {
      x -= xlogx(counts[j]);
      total += counts[j];
    }
    return x + xlogx(total);
  }

  /**
   * Tests if a is smaller or equal to b.
   *
   * @param a a double
   * @param b a double
   */
  public static boolean smOrEq(double a,double b) {
    
    return (a-b < SMALL);
  }

  /**
   * Tests if a is greater or equal to b.
   *
   * @param a a double
   * @param b a double
   */
  public static boolean grOrEq(double a,double b) {
    
    return (b-a < SMALL);
  }
  
  /**
   * Tests if a is smaller than b.
   *
   * @param a a double
   * @param b a double
   */
  public static boolean sm(double a,double b) {
    
    return (b-a > SMALL);
  }

  /**
   * Tests if a is smaller than b.
   *
   * @param a a double
   * @param b a double 
   */
  public static boolean gr(double a,double b) {
    
    return (a-b > SMALL);
  }

  /**
   * Returns the logarithm of a for base 2.
   *
   * @param a a double
   */
  public static double log2(double a) {
    
    return Math.log(a) / log2;
  }

  /**
   * Returns index of maximum element in a given
   * array of doubles. First maximum is returned.
   *
   * @param doubles the array of doubles
   * @return the index of the maximum element
   */
  public static int maxIndex(double [] doubles) {

    double maximum = 0;
    int maxIndex = 0;

    for (int i = 0; i < doubles.length; i++) {
      if ((i == 0) || (doubles[i] > maximum)) {
    maxIndex = i;
    maximum = doubles[i];
      }
    }

    return maxIndex;
  }

  /**
   * Returns index of maximum element in a given
   * array of integers. First maximum is returned.
   *
   * @param ints the array of integers
   * @return the index of the maximum element
   */
  public static int maxIndex(int [] ints) {

    int maximum = 0;
    int maxIndex = 0;

    for (int i = 0; i < ints.length; i++) {
      if ((i == 0) || (ints[i] > maximum)) {
    maxIndex = i;
    maximum = ints[i];
      }
    }

    return maxIndex;
  }

  /**
   * Computes the mean for an array of doubles.
   *
   * @param vector the array
   * @return the mean
   */
  public static double mean(double[] vector) {
  
    double sum = 0;

    if (vector.length == 0) {
      return 0;
    }
    for (int i = 0; i < vector.length; i++) {
      sum += vector[i];
    }
    return sum / (double) vector.length;
  }

  /**
   * Returns index of minimum element in a given
   * array of integers. First minimum is returned.
   *
   * @param ints the array of integers
   * @return the index of the minimum element
   */
  public static int minIndex(int [] ints) {

    int minimum = 0;
    int minIndex = 0;

    for (int i = 0; i < ints.length; i++) {
      if ((i == 0) || (ints[i] < minimum)) {
    minIndex = i;
    minimum = ints[i];
      }
    }

    return minIndex;
  }

  /**
   * Returns index of minimum element in a given
   * array of doubles. First minimum is returned.
   *
   * @param doubles the array of doubles
   * @return the index of the minimum element
   */
  public static int minIndex(double [] doubles) {

    double minimum = 0;
    int minIndex = 0;

    for (int i = 0; i < doubles.length; i++) {
      if ((i == 0) || (doubles[i] < minimum)) {
    minIndex = i;
    minimum = doubles[i];
      }
    }

    return minIndex;
  }

  /**
   * Normalizes the doubles in the array by their sum.
   *
   * @param doubles the array of double
   * @exception IllegalArgumentException if sum is Zero or NaN
   */
  public static void normalize(double[] doubles) {

    double sum = 0;
    for (int i = 0; i < doubles.length; i++) {
      sum += doubles[i];
    }
    normalize(doubles, sum);
  }

  /**
   * Normalizes the doubles in the array using the given value.
   *
   * @param doubles the array of double
   * @param sum the value by which the doubles are to be normalized
   * @exception IllegalArgumentException if sum is zero or NaN
   */
  public static void normalize(double[] doubles, double sum) {

    if (Double.isNaN(sum)) {
      throw new IllegalArgumentException("Can't normalize array. Sum is NaN.");
    }
    if (sum == 0) {
      // Maybe this should just be a return.
      throw new IllegalArgumentException("Can't normalize array. Sum is zero.");
    }
    for (int i = 0; i < doubles.length; i++) {
      doubles[i] /= sum;
    }
  }

  /**
   * Rounds a double to the next nearest integer value. The JDK version
   * of it doesn't work properly.
   *
   * @param value the double value
   * @return the resulting integer value
   */
  public static int round(double value) {

    int roundedValue = value > 0
      ? (int)(value + 0.5)
      : -(int)(Math.abs(value) + 0.5);
    
    return roundedValue;
  }

  /**
   * Rounds a double to the given number of decimal places.
   *
   * @param value the double value
   * @param afterDecimalPoint the number of digits after the decimal point
   * @return the double rounded to the given precision
   */
  public static double roundDouble(double value,int afterDecimalPoint) {

    double mask = Math.pow(10.0, (double)afterDecimalPoint);

    return (double)(Math.round(value * mask)) / mask;
  }

  /**
   * Sorts a given array of integers in ascending order and returns an 
   * array of integers with the positions of the elements of the original 
   * array in the sorted array. The sort is stable. (Equal elements remain
   * in their original order.)
   *
   * @param array this array is not changed by the method!
   * @return an array of integers with the positions in the sorted
   * array.
   */
  public static int[] sort(int [] array) {

    int [] index = new int[array.length];
    int [] newIndex = new int[array.length];
    int [] helpIndex;
    int numEqual;
    
    for (int i = 0; i < index.length; i++) {
      index[i] = i;
    }
    quickSort(array, index, 0, array.length - 1);

    // Make sort stable
    int i = 0;
    while (i < index.length) {
      numEqual = 1;
      for (int j = i + 1; ((j < index.length)
               && (array[index[i]] == array[index[j]]));
       j++) {
    numEqual++;
      }
      if (numEqual > 1) {
    helpIndex = new int[numEqual];
    for (int j = 0; j < numEqual; j++) {
      helpIndex[j] = i + j;
    }
    quickSort(index, helpIndex, 0, numEqual - 1);
    for (int j = 0; j < numEqual; j++) {
      newIndex[i + j] = index[helpIndex[j]];
    }
    i += numEqual;
      } else {
    newIndex[i] = index[i];
    i++;
      }
    }
    return newIndex;
  }

  /**
   * Sorts a given array of doubles in ascending order and returns an
   * array of integers with the positions of the elements of the
   * original array in the sorted array. NOTE THESE CHANGES: the sort
   * is no longer stable and it doesn't use safe floating-point
   * comparisons anymore. Occurrences of Double.NaN are treated as 
   * Double.MAX_VALUE
   *
   * @param array this array is not changed by the method!
   * @return an array of integers with the positions in the sorted
   * array.  
   */
  public static int[] sort(double [] array) {

    int [] index = new int[array.length];
    array = (double [])array.clone();
    for (int i = 0; i < index.length; i++) {
      index[i] = i;
      if (Double.isNaN(array[i])) {
        array[i] = Double.MAX_VALUE;
      }
    }
    quickSort(array, index, 0, array.length - 1);
    return index;
  }

  /**
   * Sorts a given array of doubles in ascending order and returns an 
   * array of integers with the positions of the elements of the original 
   * array in the sorted array. The sort is stable (Equal elements remain
   * in their original order.) Occurrences of Double.NaN are treated as 
   * Double.MAX_VALUE
   *
   * @param array this array is not changed by the method!
   * @return an array of integers with the positions in the sorted
   * array.
   */
  public static int[] stableSort(double [] array){

    int [] index = new int[array.length];
    int [] newIndex = new int[array.length];
    int [] helpIndex;
    int numEqual;
    
    array = (double [])array.clone();
    for (int i = 0; i < index.length; i++) {
      index[i] = i;
      if (Double.isNaN(array[i])) {
        array[i] = Double.MAX_VALUE;
      }
    }
    quickSort(array,index,0,array.length-1);

    // Make sort stable

    int i = 0;
    while (i < index.length) {
      numEqual = 1;
      for (int j = i+1; ((j < index.length) && Utils.eq(array[index[i]],
                            array[index[j]])); j++)
    numEqual++;
      if (numEqual > 1) {
    helpIndex = new int[numEqual];
    for (int j = 0; j < numEqual; j++)
      helpIndex[j] = i+j;
    quickSort(index, helpIndex, 0, numEqual-1);
    for (int j = 0; j < numEqual; j++) 
      newIndex[i+j] = index[helpIndex[j]];
    i += numEqual;
      } else {
    newIndex[i] = index[i];
    i++;
      }
    }

    return newIndex;
  }

  /**
   * Computes the variance for an array of doubles.
   *
   * @param vector the array
   * @return the variance
   */
  public static double variance(double[] vector) {
  
    double sum = 0, sumSquared = 0;

    if (vector.length <= 1) {
      return 0;
    }
    for (int i = 0; i < vector.length; i++) {
      sum += vector[i];
      sumSquared += (vector[i] * vector[i]);
    }
    return (sumSquared - (sum * sum / (double) vector.length)) / 
      (double) (vector.length - 1);
  }

  /**
   * Computes the sum of the elements of an array of doubles.
   *
   * @param doubles the array of double
   * @returns the sum of the elements
   */
  public static double sum(double[] doubles) {

    double sum = 0;

    for (int i = 0; i < doubles.length; i++) {
      sum += doubles[i];
    }
    return sum;
  }

  /**
   * Computes the sum of the elements of an array of integers.
   *
   * @param ints the array of integers
   * @returns the sum of the elements
   */
  public static int sum(int[] ints) {

    int sum = 0;

    for (int i = 0; i < ints.length; i++) {
      sum += ints[i];
    }
    return sum;
  }

  /**
   * Returns c*log2(c) for a given integer value c.
   *
   * @param c an integer value
   * @returns c*log2(c) (but is careful to return 0 if c is 0)
   */
  public static double xlogx(int c) {
    
    if (c == 0) {
      return 0.0;
    }
    return c * Utils.log2((double) c);
  }

  /**
   * Implements quicksort for an array of indices.
   *
   * @param array the array of integers to be sorted
   * @param index the index which should contain the positions in the
   * sorted array
   * @param lo0 the first index of the subset to be sorted
   * @param hi0 the last index of the subset to be sorted
   */
  private static void quickSort(int [] array, int [] index,
                int lo0, int hi0) {

    int lo = lo0;
    int hi = hi0;
    int mid;
    int help;
    
    if (hi0 > lo0) {
      
      // Arbitrarily establishing partition element as the midpoint of
      // the array.
      mid = array[index[(lo0 + hi0) / 2]];

      // loop through the array until indices cross
      while (lo <= hi) {
    
    // find the first element that is greater than or equal to  
    // the partition element starting from the left Index.
    while ((array[index[lo]] < mid) && (lo < hi0)) {
      ++lo;
    }
    
    // find an element that is smaller than or equal to 
    // the partition element starting from the right Index.
    while ((array[index[hi]] > mid) && (hi > lo0)) {
      --hi;
    }
    
    // if the indexes have not crossed, swap
    if (lo <= hi) {
      help = index[lo];
      index[lo] = index[hi];
      index[hi] = help;
      ++lo;
      --hi;
    }
      }
      
      // If the right index has not reached the left side of array
      // must now sort the left partition.
      if (lo0 < hi) {
    quickSort(array, index, lo0, hi);
      }
      
      // If the left index has not reached the right side of array
      // must now sort the right partition.
      if (lo < hi0) {
    quickSort(array, index, lo, hi0);
      }
    }
  }

  /**
   * Implements unsafe quicksort for an array of indices.
   *
   * @param array the array of doubles to be sorted
   * @param index the index which should contain the positions in the
   * sorted array
   * @param lo0 the first index of the subset to be sorted
   * @param hi0 the last index of the subset to be sorted
   */
  private static void quickSort(double [] array, int [] index, int lo0, int hi0) {

    int lo = lo0;
    int hi = hi0;
    double mid;
    int help;
    
    if (hi0 > lo0) {
      
      // Arbitrarily establishing partition element as the midpoint of
      // the array.
      mid = array[index[(lo0 + hi0) / 2]];

      // loop through the array until indices cross
      while (lo <= hi) {
    
    // find the first element that is greater than or equal to  
    // the partition element starting from the left Index.
    while ((array[index[lo]] < mid) && (lo < hi0)) {
      ++lo;
    }
    
    // find an element that is smaller than or equal to 
    // the partition element starting from the right Index.
    while ((array[index[hi]] > mid) && (hi > lo0)) {
      --hi;
    }
    
    // if the indexes have not crossed, swap
    if (lo <= hi) {
      help = index[lo];
      index[lo] = index[hi];
      index[hi] = help;
      ++lo;
      --hi;
    }
      }
      
      // If the right index has not reached the left side of array
      // must now sort the left partition.
      if (lo0 < hi) {
    quickSort(array, index, lo0, hi);
      }
      
      // If the left index has not reached the right side of array
      // must now sort the right partition.
      if (lo < hi0) {
    quickSort(array, index, lo, hi0);
      }
    }
  }

  /**
   * Main method for testing this class.
   *
   * @param ops some dummy options
   */
  public static void main(String[] ops) {

    double[] doubles = {4.5, 6.7, Double.NaN, 3.4, 4.8, 1.2, 3.4};
    int[] ints = {12, 6, 2, 18, 16, 6, 7, 5};

    try {

      // Option handling
      System.out.println("First option split up:");
      if (ops.length > 0) {
    String[] firstOptionSplitUp = Utils.splitOptions(ops[0]);
    for (int i = 0; i < firstOptionSplitUp.length; i ++) {
      System.out.println(firstOptionSplitUp[i]);
    }
      }                        
      System.out.println("Partitioned options: ");
      String[] partitionedOptions = Utils.partitionOptions(ops);
      for (int i  = 0; i < partitionedOptions.length; i++) {
    System.out.println(partitionedOptions[i]);
      }
      System.out.println("Get flag -f: " + Utils.getFlag('f', ops));
      System.out.println("Get option -o: " + Utils.getOption('o', ops));
      System.out.println("Checking for remaining options... ");
      Utils.checkForRemainingOptions(ops);
      
      // Statistics
      System.out.println("Original array (doubles): ");
      for (int i = 0; i < doubles.length; i++) {
    System.out.print(doubles[i] + " ");
      }
      System.out.println();
      System.out.println("Original array (ints): ");
      for (int i = 0; i < ints.length; i++) {
    System.out.print(ints[i] + " ");
      }
      System.out.println();
      System.out.println("Correlation: " + Utils.correlation(doubles, doubles, 
                                 doubles.length));
      System.out.println("Mean: " + Utils.mean(doubles));
      System.out.println("Variance: " + Utils.variance(doubles));
      System.out.println("Sum (doubles): " + Utils.sum(doubles));
      System.out.println("Sum (ints): " + Utils.sum(ints));
      System.out.println("Max index (doubles): " + Utils.maxIndex(doubles));
      System.out.println("Max index (ints): " + Utils.maxIndex(ints));
      System.out.println("Min index (doubles): " + Utils.minIndex(doubles));
      System.out.println("Min index (ints): " + Utils.minIndex(ints));
      
      // Sorting and normalizing
      System.out.println("Sorted array (doubles): ");
      int[] sorted = Utils.sort(doubles);
      for (int i = 0; i < doubles.length; i++) {
    System.out.print(doubles[sorted[i]] + " ");
      }
      System.out.println();
      System.out.println("Normalized array (doubles): ");
      Utils.normalize(doubles);
      for (int i = 0; i < doubles.length; i++) {
    System.out.print(doubles[i] + " ");
      }
      System.out.println();
      System.out.println("Normalized again (doubles): ");
      Utils.normalize(doubles, Utils.sum(doubles));
      for (int i = 0; i < doubles.length; i++) {
    System.out.print(doubles[i] + " ");
      }
      System.out.println();
      
      // Pretty-printing
      System.out.println("-4.58: " + Utils.doubleToString(-4.57826535, 2));
      System.out.println("-6.78: " + Utils.doubleToString(-6.78214234, 6,2));
      
      // Comparisons
      System.out.println("5.70001 == 5.7 ? " + Utils.eq(5.70001, 5.7));
      System.out.println("5.70001 > 5.7 ? " + Utils.gr(5.70001, 5.7));
      System.out.println("5.70001 >= 5.7 ? " + Utils.grOrEq(5.70001, 5.7));
      System.out.println("5.7 < 5.70001 ? " + Utils.sm(5.7, 5.70001));
      System.out.println("5.7 <= 5.70001 ? " + Utils.smOrEq(5.7, 5.70001));
      
      // Math
      System.out.println("Info (ints): " + Utils.info(ints));
      System.out.println("log2(4.6): " + Utils.log2(4.6));
      System.out.println("5 * log(5): " + Utils.xlogx(5));
      System.out.println("5.5 rounded: " + Utils.round(5.5));
      System.out.println("5.55555 rounded to 2 decimal places: " + 
             Utils.roundDouble(5.55555, 2));
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}