Author: psteitz
Date: Sun Mar 25 10:26:35 2007
New Revision: 522305
URL: http://svn.apache.org/viewvc?view=rev&rev=522305
Log:
Improved efficiency of evaluate method.
Modified:
jakarta/commons/proper/math/trunk/src/java/org/apache/commons/math/stat/descriptive/moment/Variance.java
Modified:
jakarta/commons/proper/math/trunk/src/java/org/apache/commons/math/stat/descriptive/moment/Variance.java
URL:
http://svn.apache.org/viewvc/jakarta/commons/proper/math/trunk/src/java/org/apache/commons/math/stat/descriptive/moment/Variance.java?view=diff&rev=522305&r1=522304&r2=522305
==============================================================================
---
jakarta/commons/proper/math/trunk/src/java/org/apache/commons/math/stat/descriptive/moment/Variance.java
(original)
+++
jakarta/commons/proper/math/trunk/src/java/org/apache/commons/math/stat/descriptive/moment/Variance.java
Sun Mar 25 10:26:35 2007
@@ -255,17 +255,18 @@
var = 0.0;
} else if (length > 1) {
double accum = 0.0;
+ double dev = 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);
+ dev = values[i] - mean;
+ accum += dev * dev;
+ accum2 += dev;
}
+ double len = (double) length;
if (isBiasCorrected) {
- var = (accum - (Math.pow(accum2, 2) / ((double) length))) /
- (double) (length - 1);
+ var = (accum - (accum2 * accum2 / len)) / (len - 1.0);
} else {
- var = (accum - (Math.pow(accum2, 2) / ((double) length))) /
- (double) length;
+ var = (accum - (accum2 * accum2 / len)) / len;
}
}
}
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