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Posted to issues@commons.apache.org by "Francis Li (JIRA)" <ji...@apache.org> on 2016/11/27 02:33:58 UTC
[jira] [Created] (MATH-1398) Support simple Arithmetic mean without
Compute correction factor in second pass?
Francis Li created MATH-1398:
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Summary: Support simple Arithmetic mean without Compute correction factor in second pass?
Key: MATH-1398
URL: https://issues.apache.org/jira/browse/MATH-1398
Project: Commons Math
Issue Type: Improvement
Environment: All
Reporter: Francis Li
The mean calculate by this function is different excel. which just sum/n as first half of function. can we provide another option to calculate normal means?
org.apache.commons.math3.stat.descriptive.moment.Mean
public double evaluate(final double[] values,final int begin, final int length)
163 throws MathIllegalArgumentException {
164 if (test(values, begin, length)) {
165 Sum sum = new Sum();
166 double sampleSize = length;
167
168 // Compute initial estimate using definitional formula
169 double xbar = sum.evaluate(values, begin, length) / sampleSize;
170
171 // Compute correction factor in second pass
172 double correction = 0;
173 for (int i = begin; i < begin + length; i++) {
174 correction += values[i] - xbar;
175 }
176 return xbar + (correction/sampleSize);
177 }
178 return Double.NaN;
179 }
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