dear R-listers, does anyone of you know whether there is any R package that features a alogarithm to calculate the sum formula from a given exact mass (as used in mass spectrometry)? thanks a lot, lukas -- Lukas Kohl Department of Chemical Ecology and Ecosystem Research http://www.ecosystem-research.netecosystem-research.net University of Vienna Althanstra?e 14, 1090 Vienna, Austr