Warning !

Soas is no longer maintained. You are strongly encouraged to switch to its successor, QSoas


How-to

You can run each fit by typing fit_x from the main soas prompt, x being the name of function you want to fit the data to. Type fit_? to get the list of available functions.

In the case of catalytic data, soas chooses initial values for the parameters to be adjusted. For non-catalytic data, your have to give (using the mouse) the positions of the peaks (follow instructions on screen).

You're then asked whether you want to modify these parameters: Do you wish to modify initial parameters (y/[n]) ?. If you answer yes, an Emacs window is opened with something like:

 -0.6350      1 !E(O/I)
 -0.6350      1 !E(I/R)
  -2.000      1 !log(k2/k0M)
 -0.1962E-07  1 !ilim/betad0
   293.0      - !Temperature
    2         - !JOB
    0         - !IPRINT
Take care modifying this file. Do not add nor remove lines
The first col contains guessed values to be adjusted.
The 2nd is 0 if parameter is fixed,
 - - - - - 1 - - - - - - - - free,
Do not modify JOB/IPRINT unless you know what you are doing.
Using EMACS, exit typing Ctrl-X Ctrl-S and Ctrl-X Ctrl-C

The user can set an initial value for any parameter and decide whether it should be free or fixed.

NB: some parameters are unacceptable for use by the fitting function (e.g. reduction potentials out of the potential limits of the data when fitting non-catalytic signals, negative values of k2/k0 when fitting log transforms of catalytic waves etc...).

The last column contains the name of the parameter to be adjusted.

The parameters JOB and IPRINT are described on the pages 31 and 33, respectively, of the guide http://www.netlib.org/odrpack/guide.ps.
Useful values of JOB are:
JOB=0: orthogonal distance regression.
JOB=2: ordinary least squares, and forward finite differences.
JOB=12: ordinary least squares, and central finite differences.
JOB=32: ordinary least squares, and user supplied derivative code.
Useful values of IPRINT are:
IPRINT=0: no report by ODRPACK, only the set of best parameters is returned after the fit has been performed.
IPRINT=-1: long initial summary, short final summary.
IPRINT=0211: no initial, long iteration, short final summaries.
IPRINT=1111: short initial, iteration and final summaries. When you exit, the fit function with the new initial parameters is evaluated and overlaid in blue.

You're asked again whether you want to modify the initial guess.

You're then asked whether you want to fit the data. Answering no makes you return to the main soas menu. Answering yes, the fit is performed, the best fit is overlaid in blue on top of the (yellow) raw data, and the list of adjusted parameter values are written:

Best parameters are :
 E(O/I)      E(I/R)      log(k2/k0M) ilim/betad0  name
 -0.5889     -0.6006      -3.079     -0.2055E-07 toto

Last, you're asked Do you wish to update the buffer with best fit ([y]/n) ?, before you are taken back to the soas prompt.

Don't forget to set the temperature using the temp command before fitting the data or by editing the file containing the initial guess.

Warning !

Soas is no longer maintained. You are strongly encouraged to switch to its successor, QSoas
Christophe Leger 2009-02-24