Utilities – Interpolate Missing Values

The Interpolate Missing Values utility is used automatically in Exponential Smoothing when there are missing values. While there is robustness against some missing values, if the number of missing values is large, then model estimation and forecast accuracy will be degraded.

Open Monthly Airline Passengers – Missing Values.xlsx (Sheet 1 tab). Ln(Airline Passengers2) have missing values at observations 50 and 100.
Click SigmaXL > Time Series Forecasting > Utilities > Interpolate Missing Values. Ensure that the entire data table is selected. If not, Use Entire Data Table. Click Next.
Select Ln(Airline Passengers2), click Numeric Time Series Data (Y) >>. Seasonal Frequency is specified as 12.
Click OK. A new sheet is created with the seasonally adjusted linear interpolated values highlighted in yellow.

Y50 is estimated as 5.254 (versus original value of 5.278). Y100 is estimated as 5.847 (versus original value of 5.852).