CXT: a programme for analysis of linear dynamic systems in the frequency domain

In this paper, the computer programme CXT (CompleX Tools for Linear Dynamic System Analysis), using the frequency response method, is described and exemplified. The method is based on the approximation of the frequency response of the linear or linearised dynamic system, measured or calculated from input-output measurements, by the frequency model of the system transfer function in the form of the ratio of two frequency-dependent polynomials. The form of the programme is sufficiently general to permit application in many areas, e.g., in modelling linear or linearised dynamic biological systems consisting of several subsystems arranged in serial and/or parallel fashion, with or without time delays. The programme is a menu-driven software taking data from a keyboard or disk file to produce outputs on a screen, printer, or disk file in tables and plots. The programme can run interactively or in an automatic tutorial mode, under DOS and/or WINDOWS. Numerical examples are taken from pharmacokinetics and indocyanine green liver function tests.