How to add elements to a plot using a knitr chunk without original markdown output?

Question

For documentary purposes, I want some code for a plot in the html-output, but not the plot. Later, I have to call the plotting code, and add something to the plot, but only

Answer 1

Chunk references in <<>> do not respect chunk options, so <> will not work. What you can do is to move the chunk option echo back to the main chunk like this:

```{r add.layer, fig.width=5, fig.height=5, echo=-1}
<>
points(x=rnorm(100,1,0.1), y=rnorm(100,0.8,0.1) )
```

echo=-1 means do not echo the first expression (as documented). This is probably what you want: