Our charts support nil data point values which may be of help here. When your data source asks for the data point of series 2 for the index relating to x-value 2011, you should be able to just set a nil y-value:
SChartDataPoint *dp = [SChartDataPoint new];
dp.xValue = //set 2011;
dp.yValue = nil;
This should result in the chart simply not rendering a y-value for that series/data point. I hope that's helpful!