Principal Components

Eigenanalysis - Coefficients

  

The principal components are the linear combinations of the original variables that account for the variance in the data. The maximum number of components extracted always equals the number of variables. The eigenvectors, which are comprised of coefficients corresponding to each variable, are used to calculate the principal component scores. The coefficients indicate the relative weight of each variable in the component. The bigger the absolute value of the coefficient, the more important the corresponding variable is in constructing the component.

Note

You must standardize the variables to obtain the correct component score.

Example Output

Variable             PC1       PC2       PC3       PC4       PC5 

Income             0.314     0.145    -0.676    -0.347    -0.241

Education          0.237     0.444    -0.401     0.240     0.622

Age                0.484    -0.135    -0.004    -0.212    -0.175

Residence          0.466    -0.277     0.091     0.116    -0.035

Employ             0.459    -0.304     0.122    -0.017    -0.014

Savings            0.404     0.219     0.366     0.436     0.143

Debt              -0.067    -0.585    -0.078    -0.281     0.681

Credit cards      -0.123    -0.452    -0.468     0.703    -0.195

 

Variable             PC6       PC7       PC8 

Income             0.494     0.018    -0.030

Education         -0.357     0.103     0.057

Age               -0.487    -0.657    -0.052

Residence         -0.085     0.487    -0.662

Employ            -0.023     0.368     0.739

Savings            0.568    -0.348    -0.017

Debt               0.245    -0.196    -0.075

Credit cards      -0.022    -0.158     0.058

Interpretation

For the loan applicant data, the first principal component's scores are computed from the original data using the coefficients listed under PC1:

PC1 = 0.314 Income + 0.237 Education + 0.484 Age + 0.466 Residence + 0.459 Employ + 0.404 Savings - 0.067 Debt - 0.123 Credit cards

The interpretation of the principal components is subjective and requires knowledge of the data:

·    Age (0.484), Residence (0.466), Employ (0.459), and Savings (0.404) have large positive loadings on component 1, so label this component Applicant Background.

·    Debt (-0.585) and Credit cards (-0.452) have large negative loadings on component 2, so label this component Credit History.

·    Income (-0.676) and Education (-0.401) have large negative loadings on Component 3, so label this component Academic and Income qualifications.