If you really love R, you should put it on your iPhone.  Apple gives the measurements for its products here. Let’s use a little grid magic with ggplot2 to make a chart for the back of your iphone similar to this.

require(grid)
require(ggplot2)

# thanks for the Apple measurements
# https://developer.apple.com/resources/cases/
x11(
  height = as.numeric(convertX(unit(58.55, "mm"), "in")),
  width = as.numeric(convertX(unit(115.15,"mm"), "in"))
)

# seems Rstudio make it hard to select a dev use until the new dev is
# Active
dev.set(which = dev.next())
# draw anything to activate our window
grid.text("my R iphone case")

# draw your most beautiful plot with ggplot2 or lattice a good example
# thanks http://sharpstatistics.co.uk/r/ggplot2-guide/
p <- ggplot(iris, aes(Sepal.Length, Sepal.Width)) + geom_point()
p + facet_grid(. ~ Species) + stat_smooth(method = "lm")

# draws rectangular and circular(camera) cutout
grid.roundrect(
  y = unit(28.975, "mm"),
  x = unit(57.275, "mm"),
  height = unit(57.95, "mm"),
  width = unit(114.55, "mm"),
  r = unit(8.17, "mm"),
  name = "iphoneback"
)
grid.circle(
  y = unit(49.78, "mm"),
  x = unit(106.45, "mm"),
  r = unit(3.46, "mm")
)

Cut and insert in or paste/tape to your case.

A little more seriously, this is a good way to test how your graph might appear on an iOS device if you have the need.  Just use the screen measurements from the Apple specs.