docs: private static double[] computePerDimensionVariances(Relation<? extends NumberVector> relation, double[] center, DBIDs neighborhood) {
      final int dim = center.length;
      double[] variances = new double[dim];
      for(DBIDIter iter = neighborhood.iter(); iter.valid(); iter.advance()) {
        NumberVector databaseObject = relation.get(iter);
        for(int d = 0; d < dim; d++) {
          final double deviation = databaseObject.doubleValue(d) - center[d];
          variances[d] += deviation * deviation;
        }
      }
      return VMath.timesEquals(variances, 1. / neighborhood.size());
    }