The ACCEL system - an introduction

The ACCEL-system is a light-weight, general purpose modelling environment for mathematical modelling. It combines some ideas from spreadsheets, Matlab, and traditional highschool mathematics. Its main features are the following:

• Named quantities and readible expressions. You write things like 'a=b+c*exp(-4*x)', and these expressions are numerically evaluated.
• Every '='-expression is in fact a functional definition: in 'a=b+c' you introduce a function that expresses 'a' in terms of the values of 'b' and 'c'.
• ACCEL assumes that a mathematical model comes about iteratively. Each time a new (functional) definition is entered, it may contain quantities that have not yet been defined. ACCEL keeps track of these in a to-do list; once the to-do list is empty, the model is executable.
• Input quantities are set by means of direct manipulation using sliders, check boxes, input text fields or buttons.
• Output can be presented visually in the form of a dynamically scrolling graph for each output quantity. Graphs of various forms are supported.
• ACCEL supports both statical and dynamical models: in evaluating expressions, quantities' earlier values can be queried, so a future state can be computed making use of present and past values of quantities.
• ACCEL comes with intuitive fully automatic sensitivity analysis, showing the relative sensitivities of output quantities as functions of input quantities.
• ACCEL has on-board genetic optimisation to deal with (statical) multiple-objective problems, using the SPEA algorithm by Sitzler et al.
• ACCEL contains an extensive online help system explaining all built-in functions and other features.
• ACCEL has a host of built-in linear algebra functions, courtesy of Peter Coxhead (http://www.cs.bham.ac.uk/~pxc/)
• Although javascript applications cannot read and write files, ACCEL models can be stored on the client computer by means of simple cut-n-paste using a text window.
• Running directly in the browser, ACCEL requires no plugins or downloads, and it is completely free of charge.

Listing:

User input:

Results: Arg.-s: Arg. of:

To Do list:

Results graph:

Help categories:

Help details:

Help text:

Demo scripts:

check units:

Relative sensitivities:

Arguments: graph

Results:

User results graph: control clamping for auto-scale argH. from: range from: argH to: range to: argV. from: nr. contours: argV to: nr. samples:

	drop-off rate Save node-locations to script