Principal Components and Classification Analysis Startup Panel - Quick Tab

Principal Components and Factor Analysis

Select the Quick tab of the Principal Components and Classification Analysis Startup Panel to access options to select four types of variables.

The PCCA module first prompts you to select two types of variables - Active and Supplementary. The former are the variables to be explained and must, therefore, be considered for computing factor axes. The supplementary variables, however, are explicative and are included only after determining the factor axes from the active variables. Next, you can select a variable that determines the status of each case as active or supplementary by using the code for active cases field (see below). Finally, you can also select a variable for grouping the cases, and these grouping labels can later be displayed in all the results spreadsheets or the plots.

Variables

Click the Variables button to display the standard variable selection dialog box in which you can select Variables for analysis (Active variables), Supplementary variables (optional), a Variable with active cases (optional), and a Grouping variable (optional). If you select a Variable with active cases, you must choose the Code for active cases (see below). Note that overlapping of the selected variables in four lists is not permitted. Also, note that the variable with active cases as well as the grouping variable need to be qualitative or grouping variables.

Remember, the active variables and cases are those that are used in the computation of the correlation or covariance matrix from which the principal components are computed. However, the supplementary variables and cases do not participate in the computations, but can later be mapped into the factor axes system (principal components) generated by the active variables and cases. See the Computational details and description of the respective Results options for additional details. Also, note that the values in the grouping variable is not used in any computation, but can later be used (optionally) to label cases (observations) in scatterplots of cases; a grouping variable is often useful to clearly identify and distinguish between different types or groups of observations in those plots.

Code for active cases

If you select a Variable with active cases, you must choose the code for active cases. To do this, double-click the Code for active cases edit window (or press the F2 key on your keyboard) to display the Variable Code Window, or type in the respective code value for the active cases.