Can't load relimp package

I don't think this will work if you're using RStudio. According to the RcmdrPlugin.DoE description:

The package provides a platform-independent GUI for design of experiments. It is implemented as a plugin to the R-Commander, which is a more general graphical user interface for statistics in R based on tcl/tk. DoE functionality can be accessed through the menu Design that is added to the R-Commander menus.

R Commander is a GUI completely separate from RStudio.

For disambiguation among R, RStudio (and any other GUI/IDE for that matter), see FAQ, below:

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