The similarity between any two EI full scan mass spectra can be measured using a variety of techniques ; one long-standing approach for approximating similarity is referred to as the dot-product, or cosine similarity. We denote the cosine similarity between mass spectra 𝑥 and 𝑦, measured with a low-resolution mass spectrometer and m/z tolerance 𝜖 #$ = 0, as 𝜃(𝑥, 𝑦, 𝜖 #$ ), and approximate the dissimilarity between any mass spectra as 𝜙 " (𝑥, 𝑦, 𝜖 #$ ) = 1 -𝜃(𝑥, 𝑦, 𝜖 #$ ).