The Gurobi R interface allows you to build an optimization model, pass the model to Gurobi, and obtain the optimization result, all from within the R environment. For those of you who are not familiar with R, it is a free language for statistical computing. Please visit the R Project web site for more information.
A quick note for new users: the convention in math programming is that variables are non-negative unless specified otherwise. You'll need to explicitly set lower bounds if you want variables to be able to take negative values.
The Gurobi R API