in src/main/java/com/google/solutions/df/log/aggregations/common/Util.java [178:186]
public static double calculateStdDeviation(double[] inputVector, double[] featureVector) {
double[] differences =
IntStream.range(0, inputVector.length)
.mapToDouble(i -> inputVector[i] - featureVector[i])
.toArray();
StandardDeviation sd = new StandardDeviation();
return sd.evaluate(differences);
}