HIT <- function(R0) 1 - 1/R0
p <- ggplot(data.frame(R0=c(1, 10)), aes(x=R0)) +
  stat_function(fun=HIT) +
  scale_x_continuous(limits=c(1, 10), breaks=seq(1, 10, by=1)) +
  scale_y_continuous(limits=c(0, 1), breaks=seq(0, 1, by=.2)) +
  labs(x=TeX("$\\mathit{R}_0$"),
       y=TeX("$\\mathrm{HIT} = 1 - 1/\\mathit{R}_0$"),
       title="Herd Immunity Threshold") +
  theme_minimal(base_family = "Times")

svg(filename="herd-immunity-threshold.svg")
plot(p)
dev.off()