[tor-dev] Better relay uptime visualisation

Philipp Winter phw at nymity.ch
Tue Dec 8 16:26:50 UTC 2015

On Mon, Dec 07, 2015 at 01:44:47PM -0800, David Fifield wrote:
> On Mon, Dec 07, 2015 at 02:51:23PM -0500, Philipp Winter wrote:
> > I spent some time improving the existing relay uptime visualisation [0].
> > Inspired by a research paper [1], the new algorithm uses single-linkage
> > clustering with Pearson's correlation coefficient as distance function.
> > The idea is that relays are grouped next to each other if their uptime
> > (basically a binary sequence) is highly correlated.  Check out the
> > following gallery.  It contains monthly relay uptime images, dating back
> > to 2007:
> > <https://nymity.ch/sybilhunting/uptime-visualisation/>
> How about just taking the XOR of two sequences as the distance?

Here's Nov 2015, with XOR as distance:

> It would be interesting to know if there are any near-perfect
> anticorrelations; i.e., one relay starts when another stops.

It looks like there's many of them.  So far, I calculated the
correlation as 1 - Pearson(s1,s2) because I'm only interested in
positively correlated sequences.  Here's an uptime image with
Pearson(s1,s2) as distance function, so positive correlation is
considered just as much as negative correlation.  Have a look at the
leftmost part:


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