collapse version 2.1.7

• The collapse article is now published in the Journal of Statistical Software: https://doi.org/10.18637/jss.v116.i01. This article is now the primary citation for academic use of collapse. It is also a great reference to quickly and thoroughly understand the package. citation("collapse") was also updated in this regard. The APA-style citation is:

  Krantz, S. (2026). collapse: Advanced and fast statistical computing and data transformation in R. Journal of Statistical Software, 116(1), 1–38. https://doi.org/10.18637/jss.v116.i01

• Performance improvements to fsum() and fmean() in the non-grouped case through multiple-accumulator SIMD optimizations, particularly benefiting systems without OpenMP support. fsum() sees ~2x speedup and fmean() ~7x speedup on such systems, with smaller but notable gains on systems with OpenMP. Thanks @TylerSagendorf for the implementation and benchmarking (#824, #828, #832, #833).

• GRP.default() gains a drop = TRUE argument. Setting drop = FALSE (and providing at least one factor among the grouping columns) retains all combinations of factor levels with the observed unique values of non-factor grouping columns---the full Cartesian product---similar to dplyr::group_by(.drop = FALSE). Unobserved combinations get group.sizes of 0 and group.starts of 0L. Correspondingly, fgroup_by()/gby() gain a .drop argument, and fcount()/fcountv()/collap()/collapv() gain a drop argument, enabling counts and aggregations that retain empty groups. Thanks @egoipse for the feature request (#820, #839).

• Fixed a bug in descr() that caused R to crash with a segmentation fault when called on zero-row data frames. Thanks @hatschibratschi for reporting (#831).

• Consistency with internal updates to data.table regarding growable vectors. Thanks @aitap (#809).

• Force C locale sorting in internal operations for consistency. Thanks @MichaelChirico (#815).

• Added contributor Ivan Krylov (@aitap) to package authors.