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One of the easiest ways to explore a model is to simply make
numerical experiments. These experiments can be as simple as
plotting the model response as a function of the independent
variable(s).
Over the years we have accumulated a toolbox filled with a number of useful
command-line tools for performing these experiments.
The toolbox is available as a tgz file (analyze.tgz)
for use on any system with a C compiler.

A simple example of these tools in action is is

shell> series 0 10 .1 | \
> tf x1 2.5*exp(-3.5*x1) | xmgrace -pipe

The first part of the pipe generates the independent variable values,
the second component transforms the independent variable into the
model function, in this case, an exponential. The third component
plots the data using grace (or the graphing program of your choice).
If the model is not an algebraic model, but rather described by the
solution to an ordinary or partial differential equation, then
often a simple Euler integration and its graph is adequate to give a general idea of what
the model is doing. The Section 2.4 gives an overview
of this and other numerical methods.

The bottom line is always to plot
the results, never simply look at a list of numbers. It is surprising what
a graphical representation will reveal that numbers hide.

** Next:** Formal Questions of a
** Up:** How to ask questions
** Previous:** How to ask questions
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Frank Starmer
2004-05-19