PLASPower Law Analysis and Simulation

(for Windows™ 32 bit systems.)

Copyright © 1996 – 2012 by António Ferreira. All rights reserved.

Latest version: (Mar 2011)
Download (zipped installer for MS-Windows 32 bit systems)

PLAS is a tool for modeling integrative systems in which the dynamics of change can be described or approximated by systems of ordinary differential equations (ODEs). In is particularly suitable to analyze power-law differential equations. Over the past three decades, systems with this structure have been applied successfully in numerous modeling studies. PLAS was written with the purpose of assisting researchers in the mathematical formulation and numerical evaluation of such systems.

PLAS has a style of input based on a textual declarative syntax which is very flexible and easy to learn. PLAS has also a simple and intuitive graphical interface which includes basic plotting capabilities, tabular display of results and online help. The program is particularly suitable for use in an educational environment.

PLAS is used in universities all over the world, especially in mathematical modeling courses and is included in the book “Computational Analysis of Biochemical Systems”, (by E.O.Voit, Cambridge University Press).

PLAS is freely available for download for personal and non-commercial use. (However, it is copyrighted and not “open source”). Read the license for further details.

PLAS features:

  • A standard Windows multiple document interface: multiple files can be created, opened and manipulated simultaneously in different windows contained in a common workspace.
  • A built-in text parser capable of interpreting a declarative language appropriate for describing differential systems (not restricted to power-law systems). The parser translates textual declarations into a machine-readable internal representation.
  • Starting on version 1.2, the text parser is also capable of interpreting a scripting language appropriate for automation of PLAS operation, parameter exploration and report generation.
  • Two numerical solvers: The Taylor method in logarithmic space. This is an efficient non-stiff, variable-step, variable- order solver for strictly positive power-law initial value problems. The Adams/BDF method as implemented in the LSODA routine. This is a general-purpose stiff, variable-step and variable-order solver.
  • Basic plotting capabilities to visualize results. Time plots, 2D and 3D phase-plane plots, as well as result tables can be displayed.
  • Steady-state computation: Analytical for S-systems and numerical for other power-law systems.
  • Sensitivity analysis for steady states of power-law systems, based on implicit differentiation.

Please contact the author (António Ferreira) for questions or comments.