SYSFIT SYSFITParameter estimation in steady-state systems
SYSFIT solves parameter estimation problems where the parameters are part of a system of nonlinear equations descibing e.g. a steady-state or equililibrium model. The right hand sides of the equations depend in addition on an independent variable, e.g. a concentration. Special applications are receptor-ligand binding models based on the mass equilibrium equation.
To evaluate the fitting criterion, the system of nonlinear equations is solved by NLPQL and the solution is inserted into an objective function defined by the user. The outer least squares problem is solved either by subroutine DFNLP or DN2GB of Dennis, Gay and Welsch. Gradients are evaluated analytically in a numerically stable way based on the implicit function theorem.
Special features of SYSFIT are
SYSFIT consists of a double precision FORTRAN-77 subroutine for executing the least squares algorithm, where all parameters are passed through arguments. An additional main program takes over some organizational ballast and reads in all problem data. A user provided subroutine is required to evaluate the system of equations, the fitting criterion and corresponding gradients. Special binding models with up to ten ligands and receptors are implemented in addition. There exists a convenient user interface for SYSFIT called EASY-FIT running under MS-Windows 95/NT.
Take a look at the author's home page, or contact
Prof. K. Schittkowski Dept. of Mathematics University of Bayreuth 95440 Bayreuth, Germany
klaus.schittkowski@uni-bayreuth.de
K. Schittkowski, Parameter estimation in systems of nonlinear equations, Numerische Mathematik 68 (1994), pp. 129--142.
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