Relationship & trajectory figures

The figures in this part show how observations relate – to each other, to time, and across sets. A scatter plot puts two measurements against one another and lets the reader judge the association directly. A spaghetti plot follows one patient’s repeated measurements as a line, so a cohort of echo studies or serial gradients becomes a tangle of individual trajectories rather than a single average. The postage-stamp chapter takes that same longitudinal data and breaks it into a grid of small multiples, one panel per patient or per group, when the tangle gets too dense to read. The UpSet chapter closes the part by showing which combinations of conditions co-occur – the comorbidity overlaps a Venn diagram can no longer handle past three or four sets.

The postage-stamp small multiples are built from bare ggplot2 and the house theme rather than a dedicated helper; the chapter flags where that matters.