R: function to scale ggplot2, lattice or base R graph proportionally

Question

In R I always find it annoying that base R, lattice and ggplot2 plots all work with absolute point sizes for the size of text and plot symbols.

This means that if you in

Answer 1

This seems to be closer to your end goal

library(ggplot2)
p <- qplot(Sepal.Length, Petal.Length, data = iris, 
           geom=c("point","line"),
           color = Species, size = Petal.Width, alpha = I(0.7))
library(grid)
print(p, vp=viewport(gp=gpar(cex=2, lex=2)))