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Renamed internal field, added algorithm documentation. 

git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/math/trunk@141128 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Phil Steitz 2004-03-13 20:02:28 +00:00
parent 6ac0ed2d8b
commit d29a69613e
1 changed files with 65 additions and 32 deletions
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97
src/java/org/apache/commons/math/stat/univariate/rank/Percentile.java
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@ -20,38 +20,51 @@ import java.util.Arrays;
import org.apache.commons.math.stat.univariate.AbstractUnivariateStatistic;
/**
* @version $Revision: 1.14 $ $Date: 2004/03/04 04:25:09 $
* 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: 1.15 $ $Date: 2004/03/13 20:02:28 $
*/
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 @@ public class Percentile extends AbstractUnivariateStatistic implements Serializa
}
/**
* @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 @@ public class Percentile extends AbstractUnivariateStatistic implements Serializa
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 @@ public class Percentile extends AbstractUnivariateStatistic implements Serializa
}
/**
* 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;
}
}