DART-MS is an ambient ionization mass spectrometry technique that is generally not preceded by a chromatography step. Accordingly, real-world mass spectra collected with DART-MS often contain signature ions originating from more than one compound, and spectral similarity or dissimilarity between an unknown mass spectrum and a reference spectrum of a pure compound is approximated using partial pattern matching approaches . In this study, we compare pure standard library spectra to each other, which allows us to use cosine similarity (or full pattern matching) in a manner similar to Equation ( ). With the DART-MS mass spectra, 𝐸 = 3 represents all compounds with mass spectra measured at the exact same is-CID energies.