Create a valplot in R

valplot.rmd

Create two bimodal toy distributions.

```{r}
a = c(rnorm(100, 5, 2), rnorm(100, 15, 3))
b = c(rnorm(100, 3, 3), rnorm(100, 14, 1))
```

Set up the graphics environment.

We draw a density curve. `polygon` draws a filled curve, but you don’t seem to be able to control the border width.

```{r}
# These values need to be fiddled with.
xlim = c(0, 20)
ylim = c(0, 0.2)
plot(0, type = 'n', xlim = xlim, ylim = ylim, bty = 'n',
     axes = FALSE, ylab = '')
Axis(side = 1)
# Shift coordinate system upwards.
par(usr = c(xlim, -0.05, 0.15))
polygon(density(a), col = 'black', border = 'white')

# Shift coordinate system back downwards.
par(usr = c(xlim, ylim))
polygon(density(b), col = 'black', border = 'white')
```