Code to clear all plots in RStudio

dev.off() only works in an interactive session. If you're interested in implementing such behavior in a script, you should use

graphics.off()

instead.

dev.off() closes the current graphical device. This clears all of the plots for me in RStudio as long as I don't have a different graphical device open at the moment. If you do have other graphical devices open then you can use dev.list() to figure out which graphical device is RStudio's. The following should do that but I haven't tested it thoroughly.

dev.off(dev.list()["RStudioGD"])

But if you aren't doing anything else then just using dev.off() should take care of it.