scale_radius() is defunct as of plotit 1.0. Radius/size encoding is
the scale_size() domain.
Details
For bubble charts whose area should encode magnitude:
scale_size(range = c(1, 6))maps linearly to ggplot2's area-like size unit (the size domain default), orggplot2::scale_radius(...)maps to the circle radius directly (area-proportional emphasis, Vega-Lite'sscaleRadiussemantics).
References
Vega-Lite: Radius