/*
* File:  ArrayDataSet.java
*
* A class with an array instance variable 
*/

/**
 * Computes average, maximum, and standard deviation of any number of scores
 */
public class ArrayDataSet 
{
   // instance var
   private int[] scores ;          // array object variable
     
   /**
    * Creates a data set with any number of scores
    * @param theScores an array of scores to be added to the set
    */
   public ArrayDataSet(int [] theScores)
   {
      // point instance var "scores" at the array parameter
      scores = theScores ;   
   }
   
   /**
    * Returns a string containing all the scores in the DataSet
    * @return all the scores
    */
   public String toString()
   {
       String scoreString = "" ;        // create empty string

       // for each score in the set...
       for (int i = 0 ; i < scores.length ; i ++)
       {
          // ...concatenate it to scoreString
          scoreString += "  " + scores[i] ; 
       }
       return scoreString ;
   }
   
   /**
    * Returns the average of the scores in the DataSet
    * @return the average score
    */
   public double getAverage()
   {
       int sum = 0 ;
       // for each score in the DataSet
       for (int i = 0 ; i < scores.length ; i ++)
       {
           sum = sum  + scores[i] ;
       }
       return (double)sum / scores.length ;
   }
   
   /**
    * Returns the largest score in the DataSet
    * @return the largest score
    */
   public int getMaximum()
   {
       int max = scores[0];           // assume first score is largest
       
       // check all other scores
       for (int i = 1 ; i < scores.length ; i ++)
       {
           if ( scores[i] > max)      // if next score . current max...
           {
               max = scores[i] ;      // ...save as new max
           }
       }
       return max ;
   }
   
   /**
    * Computes and returns the population standard deviation
    * @return the population standard deviation
    */
   public double getStanDev()
   {
       // 1. get the average of all the scores
       double average = this.getAverage() ;
       
       // 2. compute the sum of the squares of the differences between
       //    each score and the average
       
       double sumOfSquares = 0.0 ;
       
       // for each score in the array...
       for (int i = 0 ; i < scores.length ; i ++)
       {
           double diff = scores[i] - average ;  // difference from average
           sumOfSquares += Math.pow(diff,2) ;   // add square of difference
       }                                        // to accumulator

       // 3. divide by number of scores
       double variance = sumOfSquares / scores.length ;

       // 4. standard deviation is square root of the variance
       return Math.sqrt(variance) ;
   }
}