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Y' 4 CategoricalPredictors
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If a square matrix X has a true inverse X 1 , then X + = X 1
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The pseudoinverse of a pseudoinverse is the original matrix: (X + ) + = X. 5. If dim(X) = < ⇥ =, then dim(X + )
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However, if X has full column rank then X + X = I, and if X has full row rank then XX + = I. It is always true that