Figure 3From: Building blocks for automated elucidation of metabolites: Machine learning methods for NMR predictionCoverage of chemical space by NMRShiftDB. A set of atomic descriptors were calculated for protons in Pubchem (50,000 structures/465,000 protons) (in black) and the protons with assigned shifts in the NMRShiftDB (in red, 1829 structures/18692 protons attached to carbons) and plotted using principal component analysis.Back to article page