Chapter 5 - Supplemental material: methods 269 A Although spectral alignment is typically very good, due to the alignment carried out in the raster processing, the averaged spectra were aligned to address minor differences in peak positions that might still be present. This was carried out using a fixed set of alignment points, which are listed in Supplementary Table 4. Supplementary Table 4: Points in m/Z used to align the spectra 3315 8916 15872 28293 4153 9423 16078 4457 9714 17256 4710 12868 17383 5066 13766 18631 6433 14045 21069 6631 14093 21168 7934 15131 28084 Features were defined on the mass spectra. These were defined by visual inspection of an indication representative set of spectra. A feature is an m/Z region in the mass spectrum, specified by its lower m/Z limit and its upper m/Z limit. While features were defined based on the location of mass spectral peaks in typical spectra, for any individual spectrum the feature may or may not contain a well-defined mass spectral peak. Once the features were defined, their definitions became parameters in the fully-specified test. For each feature and spectrum, a feature value was defined as the integrated area under the spectrum within the feature. For this test 282 features were defined, of which 274 were used during classifier development. The mass spectral ranges defining the 274 features used in classifier development are listed in Supplementary Table 5.
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