Recursive Least-Squares Adaptive Filters Array Algorithms Elementary Circular Rotations • Elementary Hyperbolic Rotations • Square-Root-Free and Householder Transformations • A Numerical Example Geometric Interpretation • Statistical Interpretation Geometric Interpretation • Statistical Interpretation Reducing to the Regularized Form • Time Updates Estimation Errors and the Conversion Factor • Update of the Minimum Cost Motivation • A Very Useful Lemma • The Inverse QR Algorithm • The QR Algorit