Warning !

Soas is no longer maintained.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


(b) remove interpolated Base line from non catalytic data

The non catalytic data can be corrected by interpolating the baseline under the peak from the charging current on each side of the faradaic signal. Interpolation uses a cubic spline procedure.

At least 3 markers are required to define the baseline. These markers are input clicking with the mouse.

I set the maximum number of marker to 50 because putting hundreds of markers makes no sense : a few are enough if the data are smooth enough for the analysis to be worth doing. When you put markers on each side of a peak, you assume that you can interpolate a SMOOTH polynomial under the peak...if the CV is so rough that you need many markers on each side, the base line is unlikely to be smooth under the peak...So there is hardly any way of working it out.

Using the spline interpolation to smooth or differentiate :

Smoothing: An efficient way to analyze noisy data is to put 20 Smooth markers all over the data (typing s then 0), then qUit (u) replacing data with the baseline (the data are now smoothed), and then subtract the Base line again with eXact markers and Quit replacing data with data-baseline (q).

Differentiation: Once the baseline is interpolated using the spline routine, it is literally free to compute its derivative. This can be obtained by typing d when more than 3 markers are set on the data. The derivative of the baseline (which may follow the data if the markers are put all over the potential range) is plotted in the main window instead of the raw data + baseline. Type d again to get the raw data back. If you quit while the derivative is displayed, the current buffer is updated with the derivative. Note that it is not strictly speaking the derivative of the data, but the derivative of the spline function, the latter containing only intervals of cubic polynomials ; its derivative is therefore made of intervals of second order polynomials.

This command uses the public domain spline/seval procedures from the NETLIB numerical libraries (http://www.netlib.org/sfmm/spline.f).

Warning !

Soas is no longer maintained.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