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Rewrite StatUtils to use static instances of UnivariateStatistics. Benefits? 

1.) In the future, when we establish "Factories" for these objects, we'll be able to plug implementations in, even under our static Utilities classes for these functions. 

2.) The  user can always rely on the same result, whether using the StaticUtil, Univariate Container or direct UnivariateStatistic.


git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/math/trunk@141005 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Mark R. Diggory 2003-10-16 15:59:40 +00:00
parent a4947309cd
commit 005c054edd
1 changed files with 52 additions and 105 deletions
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157
src/java/org/apache/commons/math/stat/StatUtils.java
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@ -53,14 +53,48 @@
*/ */
package org.apache.commons.math.stat; package org.apache.commons.math.stat;
import org.apache.commons.math.stat.univariate.UnivariateStatistic;
import org.apache.commons.math.stat.univariate.moment.Mean;
import org.apache.commons.math.stat.univariate.moment.Variance;
import org.apache.commons.math.stat.univariate.rank.Max;
import org.apache.commons.math.stat.univariate.rank.Min;
import org.apache.commons.math.stat.univariate.summary.Product;
import org.apache.commons.math.stat.univariate.summary.Sum;
import org.apache.commons.math.stat.univariate.summary.SumOfLogs;
import org.apache.commons.math.stat.univariate.summary.SumOfSquares;
/** /**
* StatUtils provides easy static implementations of common double[] based * StatUtils provides easy static implementations of common double[] based
* statistical methods. These return a single result value or in some cases, as * statistical methods. These return a single result value or in some cases, as
* identified in the javadoc for each method, Double.NaN. * identified in the javadoc for each method, Double.NaN.
* @version $Revision: 1.18 $ $Date: 2003/10/16 15:24:30 $ * @version $Revision: 1.19 $ $Date: 2003/10/16 15:59:40 $
*/ */
public final class StatUtils { public final class StatUtils {
/** sum */
private static UnivariateStatistic sum = new Sum();
/** sumSq */
private static UnivariateStatistic sumSq = new SumOfSquares();
/** prod */
private static UnivariateStatistic prod = new Product();
/** sumLog */
private static UnivariateStatistic sumLog = new SumOfLogs();
/** min */
private static UnivariateStatistic min = new Min();
/** max */
private static UnivariateStatistic max = new Max();
/** mean */
private static UnivariateStatistic mean = new Mean();
/** variance */
private static UnivariateStatistic variance = new Variance();
/** /**
* Private Constructor * Private Constructor
*/ */
@ -73,7 +107,7 @@ public final class StatUtils {
* @return the sum of the values or Double.NaN if the array is empty * @return the sum of the values or Double.NaN if the array is empty
*/ */
public static double sum(final double[] values) { public static double sum(final double[] values) {
return sum(values, 0, values.length); return sum.evaluate(values);
} }
/** /**
@ -87,12 +121,7 @@ public final class StatUtils {
final double[] values, final double[] values,
final int begin, final int begin,
final int length) { final int length) {
testInput(values, begin, length); return sum.evaluate(values, begin, length);
double accum = 0.0;
for (int i = begin; i < begin + length; i++) {
accum += values[i];
}
return accum;
} }
/** /**
@ -101,7 +130,7 @@ public final class StatUtils {
* @return the sum of the squared values or Double.NaN if the array is empty * @return the sum of the squared values or Double.NaN if the array is empty
*/ */
public static double sumSq(final double[] values) { public static double sumSq(final double[] values) {
return sumSq(values, 0, values.length); return sumSq.evaluate(values);
} }
/** /**
@ -115,12 +144,7 @@ public final class StatUtils {
final double[] values, final double[] values,
final int begin, final int begin,
final int length) { final int length) {
testInput(values, begin, length); return sumSq.evaluate(values, begin, length);
double accum = 0.0;
for (int i = begin; i < begin + length; i++) {
accum += Math.pow(values[i], 2.0);
}
return accum;
} }
/** /**
@ -129,7 +153,7 @@ public final class StatUtils {
* @return the product values or Double.NaN if the array is empty * @return the product values or Double.NaN if the array is empty
*/ */
public static double product(final double[] values) { public static double product(final double[] values) {
return product(values, 0, values.length); return prod.evaluate(values);
} }
/** /**
@ -143,12 +167,7 @@ public final class StatUtils {
final double[] values, final double[] values,
final int begin, final int begin,
final int length) { final int length) {
testInput(values, begin, length); return prod.evaluate(values, begin, length);
double product = 1.0;
for (int i = begin; i < begin + length; i++) {
product *= values[i];
}
return product;
} }
/** /**
@ -157,7 +176,7 @@ public final class StatUtils {
* @return the sumLog value or Double.NaN if the array is empty * @return the sumLog value or Double.NaN if the array is empty
*/ */
public static double sumLog(final double[] values) { public static double sumLog(final double[] values) {
return sumLog(values, 0, values.length); return sumLog.evaluate(values);
} }
/** /**
@ -171,12 +190,7 @@ public final class StatUtils {
final double[] values, final double[] values,
final int begin, final int begin,
final int length) { final int length) {
testInput(values, begin, length); return sumLog.evaluate(values, begin, length);
double sumLog = 0.0;
for (int i = begin; i < begin + length; i++) {
sumLog += Math.log(values[i]);
}
return sumLog;
} }
/** /**
@ -186,7 +200,7 @@ public final class StatUtils {
* @return the mean of the values or Double.NaN if the array is empty * @return the mean of the values or Double.NaN if the array is empty
*/ */
public static double mean(final double[] values) { public static double mean(final double[] values) {
return sum(values) / (double) values.length; return mean.evaluate(values);
} }
/** /**
@ -201,8 +215,7 @@ public final class StatUtils {
final double[] values, final double[] values,
final int begin, final int begin,
final int length) { final int length) {
testInput(values, begin, length); return mean.evaluate(values, begin, length);
return sum(values, begin, length) / ((double) length);
} }
/** /**
@ -219,7 +232,7 @@ public final class StatUtils {
* or 0.0 for a single value set. * or 0.0 for a single value set.
*/ */
public static double variance(final double[] values) { public static double variance(final double[] values) {
return variance(values, 0, values.length); return variance.evaluate(values);
} }
/** /**
@ -241,24 +254,7 @@ public final class StatUtils {
final double[] values, final double[] values,
final int begin, final int begin,
final int length) { final int length) {
testInput(values, begin, length); return variance.evaluate(values, begin, length);
double variance = Double.NaN;
if (values.length == 1) {
variance = 0;
} else if (values.length > 1) {
double mean = mean(values, begin, length);
double accum = 0.0;
double accum2 = 0.0;
for (int i = begin; i < begin + length; i++) {
accum += Math.pow((values[i] - mean), 2.0);
accum2 += (values[i] - mean);
}
variance =
(accum - (Math.pow(accum2, 2) / ((double) length))) /
(double) (length - 1);
}
return variance;
} }
/** /**
@ -267,7 +263,7 @@ public final class StatUtils {
* @return the maximum of the values or Double.NaN if the array is empty * @return the maximum of the values or Double.NaN if the array is empty
*/ */
public static double max(final double[] values) { public static double max(final double[] values) {
return max(values, 0, values.length); return max.evaluate(values);
} }
/** /**
@ -281,18 +277,7 @@ public final class StatUtils {
final double[] values, final double[] values,
final int begin, final int begin,
final int length) { final int length) {
testInput(values, begin, length); return max.evaluate(values, begin, length);
double max = Double.NaN;
for (int i = begin; i < begin + length; i++) {
if (i == 0) {
max = values[i];
} else {
if (max < values[i]) {
max = values[i];
}
}
}
return max;
} }
/** /**
@ -301,7 +286,7 @@ public final class StatUtils {
* @return the minimum of the values or Double.NaN if the array is empty * @return the minimum of the values or Double.NaN if the array is empty
*/ */
public static double min(final double[] values) { public static double min(final double[] values) {
return min(values, 0, values.length); return min.evaluate(values);
} }
/** /**
@ -315,45 +300,7 @@ public final class StatUtils {
final double[] values, final double[] values,
final int begin, final int begin,
final int length) { final int length) {
return min.evaluate(values, begin, length);
testInput(values, begin, length);
double min = Double.NaN;
for (int i = begin; i < begin + length; i++) {
if (i == 0) {
min = values[i];
} else {
if (min > values[i]) {
min = values[i];
}
}
}
return min;
} }
/** }
* Private testInput method used by all methods to verify the content
* of the array and indicies are correct.
* @param values Is a double[] containing the values
* @param begin processing at this point in the array
* @param length processing at this point in the array
*/
private static void testInput(
final double[] values,
final int begin,
final int length) {
if (length > values.length) {
throw new IllegalArgumentException("length > values.length");
}
if (begin + length > values.length) {
throw new IllegalArgumentException(
"begin + length > values.length");
}
if (values == null) {
throw new IllegalArgumentException("input value array is null");
}
}
}