Editing System identification (section)

===Input-output vs output-only===
System identification techniques can utilize both input and output data (e.g. [[eigensystem realization algorithm]]) or can include only the output data (e.g. [[frequency domain decomposition]]). Typically an input-output technique would be more accurate, but the input data is not always available. In addition, the final estimated responses from arbitrary inputs can be analyzed by investigating their correlation and spectral properties.<ref>{{cite book |last1=Ljung |first1=Lennart |title=Modeling and identification of dynamic systems |date=2021 |publisher=Studentlitteratur |location=Lund |isbn=9789144153452 |pages=221 |edition=Second}}</ref>