Bolding plotting characters

lwd argument
The lwd argument is most commonly used to adjust line width in functions like plot(), lines(), abline(), and other plotting functions, but it can also be used to adjust the line width of plotting characters.
  • lwd – A positive number.

Example. Below I create five plotting characters for y = 1, and then I add the same plotting characters in progressively more bolded fonts using y = 2, y = 3, y = 4, and y = 5.
>
> x <- 1:5
> max.lwd <- 5
> at1 <- rep(1, length(x))
> png("plotting-characters-with-lwd.png")
> plot(x, at1, pch = x, lwd = 1, ylim = c(0.5, max.lwd + 0.5))
> for (i in 2:max.lwd) {
+   points(x, i * at1, pch = x, lwd = i)
+ }
> dev.off()
null device 
          1 
>