Software! Math! Data! The blog of R. Sean Bowman
The blog of R. Sean Bowman

## Order statistics density approximations

November 11 2016

In distributed systems a process often needs to wait for more than one of its peers before completing some action. For example, we may send a request to 5 of our peers and require that we hear back from 3 of them before considering the action completed. Even when the distribution of round trip times for a single request is pretty simple, it’s not entirely clear what the distribution of the aggregate request will be. (To me, at least; maybe if you’re smart or know statistics well it’s simpler.) In any case, we can use a histogram to get an idea of the shape of the density function.

## D3 tables and heterogeneous nesting

August 13 2016

D3 is a Javascript library for creating charts, animations, and other visualizations. It’s awesome. One of its key features is the easy creation of a DOM heirarchy mirroring some data you’ve carefully constructed for the job. Here’s a way to create a hierarchy of elements where the elements in each level aren’t necessarily homogeneous. I used this to make a table with a header column, but I’m sure it has lots of uses.

## Simplicial Complexes from Data

February 11 2016

In a previous article, we saw how to compute the (zeroth) persistent homology of a filtered simplicial complex. But how do we obtain such a complex, anyway? Scientists and others who work with data often start with a bunch of points in a high dimensional space. What are some good ways to turn that information into a filtered simplicial complex we can compute the persistent homology from?