Correlated fragment ions of a molecule are grouped using mass spectrometry with ramps in collision energy (CE). A known molecule is fragmented and analyzed at a plurality of different collision energies using a mass spectrometer. A plurality of variables for a plurality of fragment ions are produced. Principal component analysis is performed on the plurality of variables. A number of principal components produced by the principal component analysis is selected. A subset principal component space is created having the number of principal components. A variable in the subset principal component space is selected. A spatial angle is defined around a vector extending from an origin to the variable. A set of one or more variables within the spatial angle of the vector is selected. The set is assigned to a group, if the set includes a minimum number of variables.