Workspace Node: Principal Components and Classification Analysis - Specifications - Quick Tab

The Principal Components and Classification Analysis workspace node can be accessed from the Feature Finder, the ribbon bar, or the Node Browser. The Specifications - Quick tab is displayed by default when you open the specifications dialog box.

Element Name Description
Variables Click the Variables button to display a 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 a Variable with active cases is selected, you must choose a Code for active cases (see below). Note that overlapping the selected variables in the 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.It is important to note that the active variables and cases are those 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 for additional details. Also, note that the values in the grouping variable will not be 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 a Variable with active cases is selected, you must choose the code for active cases. To do this, double-click the Code for active cases edit box (or press the F2 key on your keyboard) to display the Select codes for stratification variable dialog box, or type in the respective code value for the active cases.
Analysis based on Specify whether to compute principal components from the correlation matrix or the covariance matrix of the active variables.
Correlations Select this option button if the data need to be standardized (centered about the means as well as scaled by the standard deviations) and, for that reason, the principal components need to be computed via the correlation matrix.
Covariances Select this option button if the data need to be centered about the means only and, for that reason, the principal components need to be computed via the covariance matrix.
Compute variances Specify the way in which the variances can be computed: as the sums of squares of deviations divided by N (the valid number of cases) or N -1. If divided by N -1, the resulting variances are estimates of the population (Sigma); if divided by N, the resulting variances are descriptions of the sample only. The same argument holds for the computation of covariances. In this group box, choose to compute variances and covariances for the PCCA from the sample (select the SS/(N-1) option button) or population (select the SS/N option button).
MD deletion Select the appropriate option button from the MD deletion group box to handle the missing data for the PCCA by Casewise deletion or Mean substitution as described below.
Casewise Select this option button to include only the cases that do not contain any missing data for any of the selected variables in the analysis.
Mean substitution Select this option button to replace missing data by the means for the respective variables (for this analysis only, not in the data file). Note that the means that replace any missing data, are computed from all cases, i.e., active as well as supplementary cases. Care must be taken for interpretation of such cases.

Options / C. See Common Options.

OK Click the OK button to accept all the specifications made in the dialog box and to close it. The analysis results will be placed in the Reporting Documents node after running (updating) the project.

See also, Results - Quick tab, Results - Variables tab, Results - Cases tab, Results - Descriptives tab, and Home tab.