Tuesday

Variance and warning signals

Sebastian has several examples of dynamical systems that decrease in variance as they approach a bifurcation. In some sense this is not surprising, both are through the collapse of periodic attractors. Figure 2d in TPB paperSchreiber, 2003 has an example in a discrete system, and Figure 5a in the Ecology Letters paper (Schreiber & Rudolf, 2008) has a continuous-time example. Consider for instance the supercritical Hopf bifurcation, in which a stable limit cycle vanishes into an unstable node, as in a van der Pol oscillator,

\[\frac{d x}{dt} = -\mu(1-y^2) x-y \]

\[\frac{dy}{dt}= x \]

Reading

Further simulation examples

Yesterday’s runs often show inadequate power to distinguish even by likelihood. Trying slightly stronger signal of collapse (faster destabilization rate).

Code library updates

Improved tag and comment handling for strings, in flickr upload through socialR, thanks to Gabriel on statscicomp for this one

## basic syntax is:
paste(c("a", "b", "c"), collapse=" ")  
## lets me grab all model parameters into comment
comment <- paste(c(names(pars), ":", pars, "\\", names(sampling), ":", sampling, "nboot:", nboot), collapse=" ")

since flickr_upload protocol wants a single element string for comments and tags. Should use these to check against hashtags to ensure parameters are handled correctly. May want to incorporate into the interface somehow.

Misc

  • Created profile on National Lab Network for education/outreach after reading a rather interesting paper in PLoS (Rumala et. al. 2011) discussing the program.

  • Data management videos from Marcel, still need posting and writeup.

  • Interview with first Dean candidate 4:15-5:30.

References