Figure 4:

Three histograms of PSM mass shifts with bins of different widths (0.005, 0.001, 0.0002 Da). Kernel density estimate (KDE) is shown as red line. KDE bandwidth, which is roughly analogous to the bin size for histograms, was selected automatically without user intervention. The green histogram (0.001 bin width) looks to be the best fit for data, however this does not yet take into account the problem of selecting the histogram bin offset. Selecting too small a bin width leads to the histogram falling apart (blue). Select too large and loose the accuracy (red). Even for the best one - green - the peak’s location could not be determined to the same level of precision as with KDE.