  We present a browser application for estimating the number of frequent
patterns, in particular itemsets, as well as the pattern frequency spectrum.
The pattern frequency spectrum is defined as the function that shows for every
value of the frequency threshold $\sigma$ the number of patterns that are
frequent in a given dataset. Our demo implements a recent algorithm proposed by
the authors for finding the spectrum. The demo is 100% JavaScript, and runs in
all modern browsers. We observe that modern JavaScript engines can deliver
performance that makes it viable to run non-trivial data analysis algorithms in
browser applications.
