Figure 2.

Distributions of variation in ion intensity for (A) high and (B) low TIC precursors. As illustrated by the differences between (A) and (B), the ion variation distributions for low TIC precursors tend to be wider than those of the high TIC precursors. In both cases it is shown in bold blue, the distribution of variation in ion intensities for the 10% most intense peaks in library spectra and in bold red, the distribution of variation in ion intensities for the 10% least intense peaks in library spectra, with other deciles shown in between. Note that the width of the distributions for the top decile distribution is markedly narrower than the bottom decile distribution suggesting the need to model the variation of ion intensity differently depending upon a peak’s intensity in the library spectrum. It should also be noted that the lowest decile distribution shown in (B) in red is not centered at 0 log fold variation due to the significantly higher deletion percentage (C) of the lowest decile library peaks in low TIC precursors. The deletion of these peaks caused all other peaks in the spectrum to increase in normalized intensity, for the entire spectrum is normalized to Euclidean Norm 1, thus causing a shift in the specific ion variation distribution.