# Warning !

**Soas** is no longer maintained. You
are

**strongly** encouraged to switch to its
successor,

QSoas
##

fit_arb: Fitting to a user-defined function.

Type `fig_arb`, and type in the function you want to use to fit
the data. You may use certain constants in the formula, which are
reminded:

The following constants are available
T : The absolute temperature
F : The faraday constant
f : F/RT
f(x) =exp(b*x + c*sqrt(x))

Soas detects automatically the unkown parameters in the
expression. You can modify them as usual before the fit; this is
actually recommended, as, unlike standard functions where Soas tries
to provide sane default values for parameters, there is no way to do
so for arbitrary functions.

The model function can call any of the following elementary functions:
exp, ln, sin, cos, tan, sqrt, asin, acos, atan, cosh, sinh, tanh, erf,
gamma, heavy. ``**'' is the symbol for exponentiation.

Christophe Leger
2009-02-24