Dear all, I have sales data that is grouped by company and year. I would like to "forecast" sales data within the sample so that I could compare the predicted sales figures with the actual sales data. For example, the data spans from 1984 to 2015 for many companies and I would like to calculate the predicted sales with a exponential smoothing procedure in 1988 from actual sales of the four previous years (1984-1987) and continue this throughout all available years so I would have a sales value for 1988 (from 1984-1987), 1989 (from 1985-1988) and so forth. So far I have been able to forecast data for the "next" year (in this case 2016) but I do not know how to set the forecast window so that it would move in 4-year increments. Thank you, Pieter
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