How to calculate de Annual Open?

Hi,

I want to calculate the Annual Open and I use this code to draw the brown line:

            var _marketdata = MarketData.GetSeries(TimeFrame);
            int _currentyear = _marketdata.OpenTime[index].Year;
            int _previousyear = _marketdata.OpenTime[index - 1].Year;
            double _openyear;

            if (_currentyear != _previousyear)
                _openyear = _marketdata.Open.LastValue;

But I've inconsistent values, because the data is not charged. See this example in the DAX:

Is there any way to charge all the annual data? Or any best way to calculate the annual open?

Thanks and regards