The means vector is now always converted into an n x 1 matrix. The argument to mxData continues to accept an R numeric vector (in fact, I don't think the mxData function currently will accept a matrix for the means argument). But the means are now always stored as an n x 1 matrix. We had some sloppiness in the R interface where sometimes it was n x 1 and sometimes it was 1 x n. I updated the test suite in light of these changes, but I did not update the /docs. UPDATE: I modified docs/source/OpenMxTutorial.rst and some more web documentation to reflect this change http://openmx.psyc.virginia.edu/dev/changeset/760 .