[MATH-1398] Support simple Arithmetic mean without Compute correction factor in second pass?

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Fix Version/s: 4.X
• Labels: easyfix

Environment

All

• Assignee: Unassigned
• Reporter: Francis Li
• Created: 27/Nov/16 02:33
• Updated: 18/Apr/17 15:19

Description

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 }