Report: Input Control and Line Chart
Input control for YEAR with values 2012, 2013, 2014, 2015.
Line chart having actual data (4 years) along with Forecasting ( triple exponential smoothing method)
Default values: All YEAR values are selected.
Scenario:
When I select only 1 year, say 2015, then I get error message saying at least 16 data points are required.
Now if I again remove filter, (i.e. select all values) on YEAR then Forecasting data DISAPPEARS.... 
Query:
Is it some kind of bug or I am missing something 