FSID is an open source toolbox, implemented in the Python, Julia and Matlab programming languages. The toolbox provides scripts which estimate linear multi-input multi-output state-space models from sample data using frequency-domain subspace algorithms. Algorithms which estimate models based on samples of the transfer function matrix as well as frequency domain input and output vectors are provided. The algorithms can be used for discrete-time models, continuous-time models as well as for approximation of rational matrices functions from samples corresponding to arbitrary points in the complex plane. To reduce the computational complexity for the estimation algorithms, an accelerated algorithm is provided which evaluate the state-space realization of the transfer function matrix at arbitrary points. The toolbox is compatible with Python 2.7+ as well as Python 3.0+ and Julia 1.0-1.5 and Matlab.

The Python implementation is contained in file python/fsid.py. The Julia implementation reside in subfolder julia as package. The python script python/examples_fsid.py illustrates the use of the toolbox. Brief documentation is provided in python/fsid_v1.pdf. The Matlab implementation is in folder matlab with main scripts gfdsid.m, fdsid.m and ffsid.m with example of use in example.m.