Eigenfunction construction for the Koopman operator: Application of subspace methods and the construction of derived bilinear models

<br/>We expand on the framework by Korda and Mezic (2020) to construct eigenfunctions directly from data by exploiting the eigenfunction PDE, guaranteeing closure and eliminating the need for a prior data dictionary. <br/>The constructed models are extended to forced systems through the multi-step prediction error of a linear state-space model....