Regularization networks are nonparametric estimators obtained from the appl
ication of Tychonov regularization or Bayes estimation to the hypersurface
reconstruction problem, Their main drawback is that the computation of the
weights scales as O(n(3)) where n is the number of data. In this paper, we
show that for a class of monodimensional problems, the complexity can be re
duced to O(n) by a suitable algorithm based on spectral factorization and K
alman filtering, Moreover, the procedure applies also to smoothing splines.