VM TTR values

[MarcoP]

I find it very,very hard to believe it's possible to arbitrarily write a text with properties that generate such perfect curves, neither deliberately in a manuscript with meaning nor as pseudorandom nonsense.

Hi Bernd, in my opinion, the perfect curves are largely the result of normalization. This plot shows non-normalized data for Q20 and two of Koen's text. I also include an edited version of the Latin text (in green), where I replaced each occurrence of "ad" with "ad ad": the frequency of "ad" is close to 1%, so this produces a 1% word reduplication rate, similar to what we see in the VMS.
   
It is clear that, without normalization, results from small windows are unreadable.

This plot shows data normalized with this formula, where M is a MATTR measure (Y values in the first plot) and W is the window size for which M was computed:
(M-1)/(W^0.8)
Values for small windows are very close to 1: this function amplifies that difference. Vice-versa, values for large windows are made smaller. The result is that values for all windows fall in a roughly comparable range. By playing around with the 0.8 exponent, one can adjust the effect of normalization in different directions.
   

Both plots show that Q20 is close to the Latin text for larger windows. For small windows, Q20 has lower MATTR. As the edited Latin file shows, this is likely due to the repetition of consecutive words, whose impact is considerable at W=3 and gradually disappears as windows get larger and larger.

In conclusion, unless I messed up something (which is totally possible), Q20 appears to behave like a relatively high-MATTR text (an highly inflected language like Latin) together with a high rate of reduplication (which is not observed in any European language).

As Koen has shown, another way to produce a similar distribution is to shuffle words in a text: in my opinion, this could support the idea of a pseudorandom text.