A mathematical approach to double words, conditional logic and the missing pages

[Vuk88]

To test this, I applied Machine Learning algorithms (Logistic Regression and LSA) to analyze the words that immediately precede these doubles, looking for a mathematical correlation.

Either I don't understand what "immediately precede these doubles" means or something is seriously wrong with the "triggers" sy, chaiin, dchy, qokchol: they never precede a reduplication.

In paragraphs of RF1b the most frequent words preceding a reduplication are daiin (8, all in Currier A), qokedy (8, all in Currier B), chedy (6, all in Currier B)...

You are absolutely right, and I thank you for pointing this out.
 I used the word 'precede', which was a very poor choice of words on my part and caused this misunderstanding.
The Logistic Regression model I used operates at the entire page level (a Bag-of-Words approach), not at the physically adjacent n-gram level. So, what the algorithm actually found is that words like cthom, shees, saiin (the red 'triggers') represent the 'macro-dialect' of those specific sections. They heavily co-occur on the exact same pages where double words are found, while words like sy, chaiin, dchy (the blue 'inhibitors') almost never appear on those pages.
Your manual check was of great help. If my algorithm had only found a specific grammatical word physically attached to the double, it would have just been a local syntax rule. But having found an entire vocabulary that turns 'on' and 'off' depending on whether or not double words are present on the page, the model essentially demonstrates mathematically that the Voynich is written in completely isolated and modular blocks. The text is rigidly partitioned.
I was wrong to call them words that 'precede' the doubles; in reality, they are words that simply 'co-occur on the same page'. Your manual count of the immediately adjacent words (like daiin and chedy) is correct for n-grams. You looked at the local syntax (what is physically attached to the double), while my algorithm mapped the global modularity of the page. Apologies again for the confusion with my wording, and many thanks to your watchful eye.