The cosine similarity between the vector constructed of relative intensities above the noise threshold from the library spectra and the vector constructed with relative intensities from 'matching' in the corresponding mixture spectrum, where matching implies the peak in the mixture closest (in m/z) to the library spectrum within a mass tolerance window (±2𝜖). Note that the vector representing the mixture could have zero valued entries. The reported number is a simple arithmetic average computed based on number of available fragmentation spectra compared.