docs: public static /*@pure@*/ double variance(double[] vector) {
    
      double sum = 0, sumSquared = 0;
  
      if (vector.length <= 1) {
        return 0;
      }
      for (int i = 0; i < vector.length; i++) {
        sum += vector[i];
        sumSquared += (vector[i] * vector[i]);
      }
      double result = (sumSquared - (sum * sum / (double) vector.length)) / 
        (double) (vector.length - 1);
  
      // We don't like negative variance
      if (result < 0) {
        return 0;
      } else {
        return result;
      }
    }