How do I calculate Allan Variance (maybe for pulsars)? I am studying pulsar timing this summer and have come across many Allan Deviation plots that include several popular clocks alongside pulsar measurements, like this one by N. Ashby and D.A. Howe: 

I am unclear as to where to start. What equation would be appropriate? I have pulsar timing data from the NANOGrav Public Data Set, which I am able to view through Tempo2 (aka will be able to view it as soon as I figure out how Tempo2 works). If there is other software anyone would recommend for this task that would also be helpful.

I am also unsure where the data for the other clocks would be publicly available. I am hoping a scientist who has done a similar calculation can point me in the right direction.
So, after some discussion and paper reading I learned of the sigma_z calculation in this paper by Matsakis, Taylor, and Eubanks. Several astronomers recommended this to me. I was also told to try out Stable32, although I'm not sure if that will work for pulsars. The code for a sigma_z calculation can be found here: sigma_z calculation. I believe this is the best method for doing what I asked.