Fig. 4.

Sparse non-negative GPCA loadings and sample PC heatmaps for the first seven PCs, which explain over 90% of the sample variance. Scaled PC loadings are superimposed on the average scaled spectra of neural stem cells, neurons, microglia and ‘Glia’, which includes oligodendrocytes and astrocytes. Sparse non-negative GPCA loadings reveal important patterns across the samples and spikes in the loadings denote the location of peaks that vary greatly across the samples. For example, PC3 exhibits peaks that have higher intensities in neural stem cells, while the peaks selected by PC5 have higher concentrations in microglia.