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SAS/Ets 9.22 User's Guide 270. Provides detailed reference material for using SAS/ETS software and guides you through the analysis and forecasting of features such as univariate and multivariate time series, cross-sectional time series, seasonal adjustments, multiequational nonlinear models, discrete choice models, limited dependent variable models, portfolio analysis, and generation of financial reports, with introductory and advanced examples for each procedure. You can also find complete information about two easy-to-use point-and-click applications: the Time Series Forecasting System, for automatic and interactive time series modeling and forecasting, and the Investment Analysis System, for time-value of money analysis of a variety of investments | 2682 F Chapter 41 Specifying Forecasting Models Figure 41.1 Automobile Sales Series Select Diagnose Series from the Tools menu. You can do this from the Develop Models window or from the Time Series Viewer window. Figure 41.2 shows this from the Develop Models window. Series Diagnostics F 2683 Figure 41.2 Selecting Series Diagnostics This opens the Series Diagnostics window as shown in Figure 41.3. 2684 F Chapter 41 Specifying Forecasting Models Figure 41.3 Series Diagnostics Window Each of the three series characteristics need for log transformation presence of a trend and seasonality has a set of options for Yes No and Maybe. Yes indicates that the series has the characteristic and that forecasting models fit to the series should be able to model and predict this behavior. No indicates that you do not need to consider forecasting models designed to predict series with this characteristic. Maybe indicates that models with and without the characteristic should be considered. Initially all these values are set to Maybe. To have the system diagnose the series characteristics select the Automatic Series Diagnostics button. This runs the diagnostic routines described in Chapter 46 Forecasting Process Details and sets the options according to the results. In this example Trend and Seasonality are changed from Maybe to Yes while Log Transform remains set to Maybe. These diagnostic criteria affect the models displayed when you use the Models to Fit window or the Automatic Model Selection model-fitting options described in the following section. You can set the criteria manually according to your judgment by selecting any of the options whether you have used the Automatic Series Diagnostics button or not. For this exercise leave them as set by the automatic diagnostics. Select the OK button to close the Series Diagnostics .
