The error shows:
package ‘gurobi’ was installed by an R version with different internals; it needs to be reinstalled for use with this R version
I tried to delete the library file of gurobi, but it doesn't work.
I also tried:
install.packages("gurobi", type = "source",repos = "C:/gurobi800/win64/R/gurobi_8.0-0.zip"), doesn't work either.
Thank you for help.