TTR Analysis, Observed vs. Reference Curve

[Jorge_Stolfi]

For what it's worth, here are the graphs for each section.

Quite interesting, Thanks!

So it seems that Herbal and Balneological (Bio) do follow Heaps's law L(n) ≈ K n^r quite accurately, with exponent r = 1-b = 0.532 and 0.522, respectively; the "official" value being 0.5, that is , L(n) ≈ K sqrt(n).

Astro and Cosmo presumably deviate from that law because they contain many single-use words (like names of stars) embedded in the text, besides the labels on the figures.

The anomalies in Pharma and Recipes could be explained by them being formulaic (like a collection of short recipes) rather than running prose.

It is surprising that the recipe section, of all places, exhibits the greatest text diversity (lowest b-value). I would have expected the opposite.

The explanation for the uneven statistics of Astro, Cosmo, Pharma, and Recipes may be due to their diagrams/recipes being sorted by topic or nature; with some topics having many low-frequency words, others being more repetitive.

All the best, stolfi

PS.  By the way, this analysis would be clearer if the lexicon size L and the number of tokens n were plotted in log-log scale.

"Happiness to an engineer is a straight line on a log-log plot" 
--Ancient Sumerian proverb.