User`s guide

3 Linear Model Identification
the n4sid reference page), and then try to refine the initial estimate using the
iterative prediction-error method PEM (see the
pem reference page).
N4SID is faster than PEM, but is typi cally less accurate and robust, and
requires additional argumen ts that might be dif fi cult to specify.
You can use the iterative prediction-error minimization (PEM) (maximum
likelihood) algorith m for all lin e ar and nonlin e ar model type s.
3-102