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Date: 13 Mar 2004 20:02:28 -0000
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From: psteitz@apache.org
To: jakarta-commons-cvs@apache.org
Subject: cvs commit:
 jakarta-commons/math/src/java/org/apache/commons/math/stat/univariate/rank
 Percentile.java
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psteitz     2004/03/13 12:02:28

  Modified:    math/src/java/org/apache/commons/math/stat/univariate/rank
                        Percentile.java
  Log:
  Renamed internal field, added algorithm documentation.
  
  Revision  Changes    Path
  1.15      +65 -32    jakarta-commons/math/src/java/org/apache/commons/math/stat/univariate/rank/Percentile.java
  
  Index: Percentile.java
  ===================================================================
  RCS file: /home/cvs/jakarta-commons/math/src/java/org/apache/commons/math/stat/univariate/rank/Percentile.java,v
  retrieving revision 1.14
  retrieving revision 1.15
  diff -u -r1.14 -r1.15
  --- Percentile.java	4 Mar 2004 04:25:09 -0000	1.14
  +++ Percentile.java	13 Mar 2004 20:02:28 -0000	1.15
  @@ -20,38 +20,51 @@
   import org.apache.commons.math.stat.univariate.AbstractUnivariateStatistic;
   
   /**
  + * Provides percentile computation.
  + * <p>
  + * There are several commonly used methods for estimating percentiles (a.k.a. quantiles) based
  + * on sample data.  For large samples, the different methods agree closely, but when sample sizes
  + * are small, different methods will give significantly different results.  The implementation provided here
  + * follows the first estimation procedure presented
  + * <a href="http://www.itl.nist.gov/div898/handbook/prc/section2/prc252.htm">here.</a>
  + * 
    * @version $Revision$ $Date$
    */
   public class Percentile extends AbstractUnivariateStatistic implements Serializable {
   
       static final long serialVersionUID = -8091216485095130416L; 
          
  -    /** */
  -    private double percentile = 0.0;
  +    /** Determines what percentile is computed when evaluate() is activated with no quantile argument */
  +    private double quantile = 0.0;
   
       /**
  -     * Constructs a Percentile with a default percentile
  +     * Constructs a Percentile with a default quantile
        * value of 50.0.
        */
       public Percentile() {
           super();
  -        percentile = 50.0;
  +        quantile = 50.0;
       }
   
       /**
  -     * Constructs a Percentile with the specific percentile value.
  -     * @param p the percentile
  +     * Constructs a Percentile with the specific quantile value.
  +     * @param p the quantile
        */
       public Percentile(final double p) {
  -        this.percentile = p;
  +        this.quantile = p;
       }
   
       /**
  -     * Evaluates the double[] top the specified percentile.
  -     * This does not alter the interal percentile state of the
  -     * statistic.
  +     * Returns an estimate of the <code>p</code>th percentile of the values
  +     * in the <code>values</code> array.
  +     * <p>
  +     * Calls to this method do not modify the internal <code>quantile</code>
  +     * state of this statistic.
  +     * <p>
  +     * See {@link Percentile} for a description of the percentile estimation algorithm used.
  +     * 
        * @param values Is a double[] containing the values
  -     * @param p Is the percentile to evaluate to.
  +     * @param p Is the quantile to evaluate to.
        * @return the result of the evaluation or Double.NaN
        * if the array is empty
        */
  @@ -60,24 +73,42 @@
       }
   
       /**
  -     * @see org.apache.commons.math.stat.univariate.UnivariateStatistic#evaluate(double[], int, int)
  +     * Returns an estimate of the <code>quantile</code>th percentile of the values
  +     * in the <code>values</code> array.  The quantile estimated is determined by
  +     * the <code>quantile</code> property.
  +     * <p>
  +     * See {@link Percentile} for a description of the percentile estimation algorithm used.
  +     * 
  +     * @param values  array of input values
  +     * @param start  the first (0-based) element to include in the computation
  +     * @param length  the number of array elements to include
  +     * @return the result of the evaluation or Double.NaN
  +     * if the array is empty
  +     * 
        */
       public double evaluate(
           final double[] values,
           final int start,
           final int length) {
   
  -        return evaluate(values, start, length, percentile);
  +        return evaluate(values, start, length, quantile);
       }
   
  -    /**
  -     * Evaluates the double[] top the specified percentile.
  -     * This does not alter the interal percentile state of the
  -     * statistic.
  +     /**
  +     * Returns an estimate of the <code>p</code>th percentile of the values
  +     * in the <code>values</code> array, starting with the element in (0-based)
  +     * position <code>begin</code> in the array and including <code>length</code>
  +     * values.
  +     * <p>
  +     * Calls to this method do not modify the internal <code>quantile</code>
  +     * state of this statistic.
  +     * <p>
  +      * See {@link Percentile} for a description of the percentile estimation algorithm used.
  +     * 
        * @param values Is a double[] containing the values
  -     * @param begin processing at this point in the array
  -     * @param length the number of elements to include
  -     * @param p Is the percentile to evaluate to.*
  +     * @param p Is the quantile to evaluate to.
  +     * @param start  the first (0-based) element to include in the computation
  +     * @param length  the number of array elements to include
        * @return the result of the evaluation or Double.NaN
        * if the array is empty
        */
  @@ -90,7 +121,7 @@
           test(values, begin, length);
   
           if ((p > 100) || (p <= 0)) {
  -            throw new IllegalArgumentException("invalid percentile value");
  +            throw new IllegalArgumentException("invalid quantile value");
           }
           double n = (double) length;
           if (n == 0) {
  @@ -119,21 +150,23 @@
       }
   
       /**
  -     * The default internal state of this percentile can be set.
  -     * This will return that value.
  -     * @return percentile
  +     * Returns the value of the quantile field (determines what percentile is computed when evaluate()
  +     * is called with no quantile argument)
  +     * 
  +     * @return quantile
        */
  -    public double getPercentile() {
  -        return percentile;
  +    public double getQuantile() {
  +        return quantile;
       }
   
       /**
  -     * The default internal state of this percentile can be set.
  -     * This will setthat value.
  -     * @param p a value between 0 <= p <= 100
  +     * Sets the value of the quantile field (determines what percentile is computed when evaluate()
  +     * is called with no quantile argument)
  +     * 
  +     * @param p a value between 0 <= p <= 100 
        */
  -    public void setPercentile(final double p) {
  -        percentile = p;
  +    public void setQuantile(final double p) {
  +        quantile = p;
       }
   
   }
  
  
  

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