Thanks for the excellent statistics library, especially the on-line algorithms 
for the statistics object. However, I often need to partition a large 
population into subsets, obtain the statistics of each subset, and obtain the 
statistics of various unions of the subsets as well as for the entire 
population. In the past (and in other languages not as fun as Racket) I've done 
this using Chan's parallel algorithm for the mean and variance and Terriberry's 
extension of Chan's algorithm for skewness and kurtosis, so that I can keep 
running statistics on each disjoint subset and later combine them for the 
various aggregations. 

I'd like to similarly extend math/statistics to enable the summation of the 
running statistics. However, I'm not very statistics-savvy and so I'm having 
trouble following the algorithm in the update-statistics function that handles 
weighted samples. I also don't have ready access to Pébaÿ's recent papers that 
extend Terriberry's method to handle weighted samples, and I probably wouldn't 
understand Pébaÿ's paper anyway :-(

So on to my questions:

Is the algorithm used in the update-statistics function amenable to being 
extended to a parallel version? In other words, do the moments in the 
statistics structure correspond to the first through fourth central moments?

Is anyone here familiar with the extensions to the parallel algorithms that 
handle weighted samples? I'd like to support weighted samples, but I just don't 
know how to handle them.

Best regards,
-Steve

--  
Steve Byan
steveb...@me.com
Littleton, MA



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