At the developer's meeting on 1/11/13 we discussed the following:
- The group discussed taking a symposium to the Association for Psychological Science conference. Ryne Estabrook, Joshua Prikitin, Mike Hunter, and Tim Brick all expressed interest. The suggested symposium theme is along the lines of imagining various complex models at SEMs. This includes state space models, item response models, and spline regressions / mixture distributions. Talks should probably involve real data, but still be mostly about the methods.
- Joshua Pritikin added R package roxygen2 as a dependency for OpenMx. The team discussed this. The package allows documentation inside source files. The team decided that for developer functions (e.g. imx* functions) documentation in the source file should be used, but not for user functions. This means that roxygen2 will not be a depenency for OpenMx, but that developer documentation could be built with a flag to the makefile.
- Mike Hunter now has state space expectations working. They use a classical Kalman filter which is known to be numerically unstable, and will be updated to an SVD-based square root filter that is numerically stable. Currently, the test for the state space expectations (200 observations, 9 observed variables, 3 latent variables) is approximately 25x faster in OpenMx than in the R package dlm.
- Joshua Pritikin has a working IRT implementation. It is comparable in speed an accuracy to PARSCALE. It is not yet checked in because it uses an EM algorithm which OpenMx does not yet support.
- The team discussed how EM algorithms could be added to OpenMx. The team tentatively agrees on adding an mxOptimizer() function with defaults. This complements the mxExpectation and mxFitFunction functions. The team has several possible specifications for EM. To use as an example Mike Hunter will distribute an EM for exploratory factor analysis (EFA). The specifications for EM will be demo-ed on EFA and on 2PL IRT.
- Tim Brick will be writing up some brief notes on the state of multilevel so we can move forward with implementation.
- Joshua Pritikin will be setting up CRON jobs to periodically run performance testing on OpenMx: gctorture, valgrind, etc.