RGP is a simple modular Genetic Programming (GP) system build in
    pure R. In addition to general GP tasks, the system supports Symbolic
    Regression by GP through the familiar R model formula interface. GP
    individuals are represented as R expressions, an (optional) type system
    enables domain-specific function sets containing functions of diverse
    domain- and range types. A basic set of genetic operators for variation
    (mutation and crossover) and selection is provided.
Oliver Flasch, Olaf Mersmann, Thomas Bartz-Beielstein, Joerg Stork,
    Martin Zaefferer