private void buildWorkingSet(DateTime start_, DateTime end_)
    {
      var days = All.ToDays(DoubleCollationType.Sum).GetSubValues(start_, end_);
      m_daily = new DataSeries(days.Dates, days.Data, Period.Daily, m_dataType);
      
      var weeks = m_daily.ToWeeks(DoubleCollationType.Sum);
      m_weekly = new DataSeries(weeks.Dates, weeks.Data, Period.Weekly, m_dataType);
      
      var months = m_daily.ToMonths(DoubleCollationType.Sum);
      m_monthly = new DataSeries(months.Dates, months.Data, Period.Monthly, m_dataType);

      var years = months.ToYears(DoubleCollationType.Sum);
      m_yearly = new DataSeries(years.Dates, years.Data, Period.Yearly, m_dataType);
    }