/**
* Calculates the third quartile for a list of numbers in ascending order.
*
* @param values the list of values.
* @return The third quartile.
*/
public static double calculateQ3(final List values) {
double result = Double.NaN;
final int count = values.size();
if (count > 0) {
if (count % 2 == 1) {
if (count > 1) {
result = Statistics.calculateMedian(values, count / 2 + 1, count - 1);
} else {
result = Statistics.calculateMedian(values, 0, 0);
}
} else {
result = Statistics.calculateMedian(values, count / 2 + 1, count - 1);
}
}
return result;
}
/**
* Calculates the statistics required for a {@link BoxAndWhiskerItem}.
*
* <p>Any items in the list that are not instances of the <code>Number</code> class are ignored.
* Likewise, <code>null</code> values are ignored.
*
* @param values A list of numbers (a <code>null</code> list is not permitted).
* @return Box-and-whisker statistics.
*/
public static BoxAndWhiskerItem calculateBoxAndWhiskerStatistics(final List values) {
Collections.sort(values);
final double mean = Statistics.calculateMean(values);
final double median = Statistics.calculateMedian(values, false);
final double q1 = calculateQ1(values);
final double q3 = calculateQ3(values);
final double interQuartileRange = q3 - q1;
final double upperOutlierThreshold = q3 + (interQuartileRange * 1.5);
final double lowerOutlierThreshold = q1 - (interQuartileRange * 1.5);
final double upperFaroutThreshold = q3 + (interQuartileRange * 2.0);
final double lowerFaroutThreshold = q1 - (interQuartileRange * 2.0);
double minRegularValue = Double.POSITIVE_INFINITY;
double maxRegularValue = Double.NEGATIVE_INFINITY;
double minOutlier = Double.POSITIVE_INFINITY;
double maxOutlier = Double.NEGATIVE_INFINITY;
final List outliers = new ArrayList();
final Iterator iterator = values.iterator();
while (iterator.hasNext()) {
final Object object = iterator.next();
if (object != null && object instanceof Number) {
final Number number = (Number) object;
final double value = number.doubleValue();
if (value > upperOutlierThreshold) {
outliers.add(number);
if (value > maxOutlier && value <= upperFaroutThreshold) {
maxOutlier = value;
}
} else if (value < lowerOutlierThreshold) {
outliers.add(number);
if (value < minOutlier && value >= lowerFaroutThreshold) {
minOutlier = value;
}
} else {
if (minRegularValue == Double.NaN) {
minRegularValue = value;
} else {
minRegularValue = Math.min(minRegularValue, value);
}
if (maxRegularValue == Double.NaN) {
maxRegularValue = value;
} else {
maxRegularValue = Math.max(maxRegularValue, value);
}
}
}
}
minOutlier = Math.min(minOutlier, minRegularValue);
maxOutlier = Math.max(maxOutlier, maxRegularValue);
return new BoxAndWhiskerItem(
new Double(mean),
new Double(median),
new Double(q1),
new Double(q3),
new Double(minRegularValue),
new Double(maxRegularValue),
new Double(minOutlier),
new Double(maxOutlier),
outliers);
}