I am trying to fit the background shape in nmr spectra. For this I have been using the loess function so far.
First I try to identify all the peaks (which works more or less) and remove them from the spectrum. Then I try to fit the rest of the spectrum with the loess function.
My problem now is that if the removal of peaks doesn't work perfectly there are still some points left which are clearly not background.
Is there a way to tell the fit not to go over the data, i.e. having the fitted line always below the data points (which is clearly what you want from a baseline)? My hope is that, if I am able to constrain the fit to be below the data points I can find suitable parameters, so that the remaining points from the peaks are ignored.
Thanks John
