[Article] A new Timm & Schinner publication regarding the Malta conference

[ReneZ]

1) It is fatally methodologically flawed to do any sort of cluster analysis on 102 data points ("The VMS consists of 102 folios, from which 5151 pairs can be selected (excluding redundancy by symmetry, and the case of two identical folios)") in a 7000-dimensional space ("The VMS vocabulary consists of about 7000 words. Let ~v be a vector with each component representing the token frequency of one of these words."). This is due to what is known as "the curse of dimensionality" -- indeed, as one web page describing the issue (You are not allowed to view links. Register or Login to view.) points out "Too many dimensions cause every observation in your dataset to appear equidistant from all the others" (my emphasis; while that quote is talking about Euclidean distance, if T&S want to claim that the same problem doesn't exist for vector cosines I would genuinely like to see a reference and will metaphorically eat my hat on this point if they can provide one). 

Thank you! I couldn't agree more.

In fact, given the inappropriately high dimensionality of their feature space the very fact that the Bio and Recipes sections stand out in Figure 2 the way they do -- that there is any kind of signal at all in the noise, that there are any kind of distinctive clusters at all in their data -- strikes me as compelling evidence against Timm & Schinner's conclusion.

This is partly a side effect of the second major issue: the data points are the folios, and these two groups of folios stand out by having far more words than the others. This is where statistics can just barely begin to work.

Cosines are very similar to correlation. Both are the scalar product of two one-dimensional vectors, just normalised in a different way.