1. xrnet::ext_linear
    Simulated external data
    csv| json| rda| rds
    matrix|50 x
  2. xrnet::x_linear
    Simulated example data for hierarchical regularized linear regression
    csv| json| rda| rds
    matrix|200 x
  3. xrnet::y_linear
    Simulated outcome data
    json| rda| rds
    numeric