In this section we will demonstrate using the model developed on the Australian wine data in Section 3.1.1 of Time Series Analysis and Forecasting with Weka. This forecaster modeled monthly sales of the "Fortified" and "Dry-white" series. The following simple transformation loads the wine data and passes it to the Weka Forecasting step. The Weka Forecasting step uses the incoming data as historical "priming" data, that is, the data is used to populate the values of lagged variables and variables derived from the time stamp. These values are then input to the forecasting model and a forecast is produced for a user-defined number of steps beyond the end of the priming data. The step outputs the historical data followed by a number of new rows that contain the forecasted values.
Subsequent sections explain the configuration options for the step and the output that it produces in detail.
4.1 Loading/Importing a Forecasting Model
Conceptually, the UI for the Weka Forecasting step is set out in a similar fashion as the Weka Scoring plugin. The Model file tab allows a model to be loaded from the file system and configured for forecasting.
The Load/import forecaster field allows a serialized forecasting model to be loaded from a file. A path can be entered into the field directly, or the Browse button can be used to bring up a file browser dialog. If the field is left populated with a path then the forecasting model will be loaded from the file every time that the transformation is run. Alternatively, after importing a forecasting model (by pressing enter in the field after a path has been typed or by using the Browse button, if the field is cleared and the OK button pressed then the model will be stored in the XML ".ktr" file or in the repository (if one is being used).
The Number of steps to forecast field allows the user to specify how many time steps into the future the model will produce predictions for. In this example we have entered "24" in order to get a monthly forecast out to 24 months beyond the end of the incoming priming data.