I get the following message “Warning, this will compute PCA on some selected derived columns, proceed?” when I try and run the PCA tool. What does this mean?

A: This message is mainly in place to prevent users from performing a PCA calculation and then running it again without realising that the Selected Variables dialog has been updated with the  PCA columns from the previous calculation.  Therefore the new PCA calculation would be using the previous PCA columns as the input columns.  Go back into the Select Variables dialog and make sure that the correct variables are selected and then continue.

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