The R package of assignR is now officially released in R CRAN (https://cran.r-project.org/web/packages/assignR)!
Github: https://github.com/SPATIAL-Lab/assignR
It is developed by working with Gabe Bowen @ University of Utah.
It includes routines for re-scaling isotope maps using known-origin tissue isotope data, assigning origin of unknown samples, and summarizing and assessing assignment results
The paper out of this :
Ma, C., Vander Zanden, H.B., Wunder, M.B. and Bowen, G.J., 2020. assignR: An R package for isotope‐based geographic assignment. Methods in Ecology and Evolution. https://doi.org/10.1111/2041-210X.13426