CRAN release plm 2.6-7:

Minor fix due to a warning on CRAN triggered by rbibutils' better checking of REFERENCES.bib

Fix release, no new features,
afc1ca9

mainly fixes for handling of FD models and some around pgmm/mtest.

mostly new features and speed improvement for pvcm, many minors

Mostly speed-up and little maintenance

Main innovations are thepredict() function (also working for FE models) and the speed-ups in the group-wise model estimation functionspcce(),pggls(),pmg(), and test functionscipstest(),pcdtest().

mainly to pacify CRAN checks due to R-devel deprecatingdefault.stringsAsFactors()

Make optional speed-up the default

CRAN release