What the document array can be compressed to is the length distribution

What the document array can be compressed to is the length distribution

The zeroth-order entropy of the document array, for four collections of 32 documents and 8,192 characters. The array holds each document once per character it contributed, so its symbol distribution is the length distribution and nothing else. On equal-length documents H0 is 5.000 against a ceiling of log2 32 = 5.000 — the two are the same number, and a wavelet tree over that array is 100.0% of the plain n⌈log₂ d⌉ array, which is to say it saves nothing. On a collection where one document holds four fifths of the text H0 falls to 1.688 and the array to 39.5%. The dashed line is the ceiling every row is measured against.

Drawn at 700 × 236, wide on the page. Everything above is what document-array returns with no arguments; the caption is the generator's own, computed from the numbers in the drawing rather than written beside it.

14 essays call document-array. The drawing above is what it returns with no arguments at all; every call below passes it something, because a placement that passes nothing draws whichever member of the family the generator happens to default to rather than the one its essay argues about — which is what optcheck and figfill exist to catch.