private void Summation()
    {
        _sum    = null;
        _abssum = null;
        _counts = 0;
        
        for (DataMeme dm : _items)
        {
            //_sum    = _sum == null      ? dm.asDouble() : (_sum + dm.asDouble());
            //_abssum = _abssum == null   ? Math.abs(dm.asDouble()) : (_abssum + Math.abs(dm.asDouble()));
            
            if (dm.asDouble() != null)
            {
                _sum    = _sum == null      ? dm.asDouble() : (_sum + dm.asDouble());
                _abssum = _abssum == null   ? Math.abs(dm.asDouble()) : (_abssum + Math.abs(dm.asDouble()));
            }
            
            _counts += dm.getCount();
        }
    }