C&RT Quick Specs

Select Quick specs dialog as the Specification method on the General Classification and Regression Trees Startup Panel - Quick tab and click the OK button to display the Quick specs dialog box. If Standard C&RT was selected as the Type of analysis, the Quick Specs dialog box is titled Standard C&RT. If C&RT with coded design was selected as the Type of analysis, the Quick specs dialog box is titled General C&RT General linear models.

The Quick specs dialog box contains five tabs: Quick, Classification, Stopping, Validation, and Advanced. In practically all cases, the most efficient way to write C&RT syntax is to use the Quick specs method, and then click the Syntax editor button in the dialog box to translate the selected specifications to the command syntax. This can further be edited and updated as and when required.

OK. Click the OK button to run the analysis and display the GC&RT Results dialog box. Note that if you have not already specified variables, a variable selection dialog box will first be displayed when you click this button.

Cancel. Click the Cancel button to close the dialog box without performing an analysis.

Options. Click the Options button to display the Options menu.

Select Cases. Click the Select Cases button to display the Analysis/Graph Case Selection Conditions dialog box, which is used to create conditions for which cases will be included (or excluded) in the current analysis. More information is available in the case selection conditions overview, syntax summary, and dialog description.

W. Click the W (Weight) button to display the Analysis/Graph Case Weights dialog box, which is used to adjust the contribution of individual cases to the outcome of the current analysis by weighting those cases in proportion to the values of a selected variable.

Syntax editor. Click the Syntax editor button to display the General Classification and Regression Trees Syntax Editor, which contains various options for specifying designs and for modifying various parameters of the computational procedures. You can also open an existing text file with command syntax, or save syntax in a file for future repetitive use. Refer to the General Classification/Regression Tree Models Syntax Overview  for additional details. Note that selecting Analysis syntax editor automatically moves the Type of analysis selection to C&RT with coded design.

Note: Missing data. Missing data in predictor variables are handled differently in the C&RT module, as compared to  the Interactive Trees module. Because the Interactive Trees module does not support ANCOVA-like design matrices, it is more flexible in the handling of missing data. Specifically, in C&RT, observations with missing data in any predictor variable are excluded from the tree-building process itself (even if surrogates are requested; these surrogates are only used to compute predicted values or classifications); in Interactive Trees, variables (and missing data for those variables) can be considered one-by-one, so observations with missing data in the predictors are only excluded from the tree building process, if those variables are chosen for splits and no suitable surrogate was requested or selected. Refer also to Missing Data in GC&RT, GCHAID, and Interactive Trees for additional details.