## 521 and 522: X Modes Options

Prompts for the maximum and the minimum numbers of X modes are given automatically after opening an X input file when using CCA or PCR, but these values can be reset from the X modes options menu item. Note that changing the number of X modes will require CPT to reset if results have been calculated. For more details on specifying the numbers of modes see X and Y modes .

The maximum number of X modes cannot exceed the minimum of the number of the number of X variables and one less than the length of the cross-validated training sample. The cross-validated training sample is the length of the training data minus the length of the cross-validation window.

By default the principal components are calculated using the correlation matrix (the analysis is based on the standardised anomalies). However, it is possible to base the analysis on either the variance-covariance matrix (the anomalies) or the sums of squares and cross-products matrix (the raw values). To set the method for calculating the X modes, click on the "Advanced" button, and then choose the required option.