Wraps some of the matrix exponentiation utilities from EXPOKIT, a Fortran 77 library that is widely recommended for matrix exponentiation (Sidje RB, 1998. "Expokit: A Software Package for Computing Matrix Exponentials." ACM Trans. Math. Softw. 24(1): 130-156). EXPOKIT includes functions for exponentiating both small, dense matrices, and large, sparse matrices (in sparse matrices, most of the cells have value 0).
Rapid matrix exponentiation is useful in phylogenetics when we have a large number of states (as we do when we are inferring the history of transitions between the possible geographic ranges of a species), but is probably useful in other ways as well.
NOTE: As of 2018-10-03, a new version of rexpokit, 0.26.6, has been accepted on CRAN. This version fixes warnings due to upgrades in CRAN's FORTRAN compilers, and more importantly, removes some dependencies previously needed by cladoRcpp/BioGeoBEARS. CRAN version is here, binaries should be available in a few days: https://cran.r-project.org/package=rexpokit
Zenodo link for release: https://zenodo.org/badge/latestdoi/17001945
Zenodo DOI for release: http://dx.doi.org/10.5281/zenodo.1442889