Principal Components and Classification Analysis Results - Quick Tab

Principal Components and Factor Analysis

Select the Quick tab of the Principal Components and Classification Analysis Results dialog box to access options to produce PCCA results pertaining to variables and cases in the current analysis. Various plotting options are available to provide a visual aid for interpretation of the results.

Factor coordinates of variables

Click the Factor coordinates of variables button to display a spreadsheet with the factor coordinates of the active and supplementary variables (if selected through the Variables button of the Principal Components Classification Analysis Startup Panel - Quick tab). To distinguish between the two types of variables in the current analysis, the supplementary variables are marked with an asterisk (*). The factor coordinates are commonly referred to as factor loadings, and provide useful information for the interpretation of the factors. Refer to the Introductory Overview for additional details.

Factor coordinates of cases

Click the Factor coordinates of cases button to display a spreadsheet with factor coordinates of cases. The spreadsheet also contains:

1. an additional column displaying the code for active and supplementary cases, if a Variable for active cases was selected through the Variables button on the Principal Components Classification Analysis Startup Panel - Quick tab;
2. an additional column (last), displaying the label defined by the grouping variable, if a Grouping variable was selected through the Variables button on the Principal Components Classification Analysis Startup Panel - Quick tab.

Note: The spreadsheet displays the factor coordinates only for the complete (valid) cases if the Casewise option button was selected in the MD deletion group box on the Principal Components Classification Analysis Startup Panel. Alternatively, if Mean substitution was selected, the mean of the corresponding variable is used in place of missing data and the spreadsheet contains the factor coordinates for all cases. The Number of factors (see the Principal Components and Classification Analysis Results dialog box) selected for the current analysis determines the number of factors for which the coordinates are computed and displayed. Note that the estimates of means and standard deviations that are used in the computation of factor coordinates of cases are computed from all valid cases, both active and supplementary. Refer to the Introductory Overview for additional details.

Eigenvalues

Click the Eigenvalues button to display a spreadsheet with the positive eigenvalues of the correlation or covariance matrix (depending on which was chosen for the analysis in the Analysis based on group box on the PCCA Startup Panel - Advanced tab). Note that the displayed eigenvalues are computed from the correlations or covariances of the active variables only, even if supplementary variables were selected through the Variables button on the PCCA Startup Panel - Quick tab.

Plot var. factor coordinates, 2D.

Click the Plot var. factor coordinates, 2D button to produce a 2D scatterplot of the current set of factor coordinates for the selected pair of factors. After you click this button the Select Two Factors for the Plot dialog box is displayed by using which you can select factors for the factor axes. Subsequent to selecting this button, you can use one of the Options for plot of factor coord. on the Principal Components and Classification Analysis Results dialog box - Variables tab.

Plot case factor coordinates, 2D

Click the Plot case factor coordinates, 2D button to produce a 2D scatterplot of the factor coordinates for the cases. The plot contains coordinates for the supplementary cases, if you selected a Variable for active cases and a valid Code for active cases on the Principal Components Classification Analysis Startup Panel - Quick tab. After you click this button, the Select Two Factors for the Plot dialog box is displayed by using which you can select factors for the factor axes. Subsequent to selecting this button, you can use one of the Options for plot of factor coord. on the Principal Components and Classification Analysis Results - Cases tab.

Scree plot

Click the Scree plot button to produce a simple line plot of the eigenvalues, called a Scree plot (Cattell, 1966). The eigenvalues in this plot look to level off at certain point.  It is recommended that no more than the number of factors to the left of this point should be computed. Note that the scree plot plots all the eigenvalues of the correlation or covariance matrix, irrespective of the Numbers of factors chosen for the current analysis (see the Principal Components and Classification Analysis Results dialog box).