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Hello everyone, I would appreciate your views on the following... For a Principal Component Analysis, we have N subjects and p variables. Say one of our variables is categorical (nominal) with categories corresponding to either 'yes', 'no', 'don't know' or 'confidential'. Would the 4 categories be entered into the PCA as 3 dummy binary variables...i.e. x1, x2 and x3 coded, perhaps, like so: x1 x2 x3 yes 1 0 0 no 0 1 0 confidential 0 0 1 don't know 0 0 0 (where, here, 'don't know' is the reference category) i.e. just as in regression, a q category variable is entered as q-1 dummy variables. Thanks so much for your views, Kim You may leave the list at any time by sending the command SIGNOFF allstat to [log in to unmask], leaving the subject line blank.