I add "fig_caption: TRUE" to the default R Notebook example:
---
title: "R Notebook"
output: html_notebook
fig_caption: TRUE
---
This is an [R Markdown](http://rmarkdown.rstudio.com) Notebook. When you execute code within the notebook, the results appear beneath the code.
Try executing this chunk by clicking the *Run* button within the chunk or by placing your cursor inside it and pressing *Ctrl+Shift+Enter*.
```{r}
plot(cars)
```
I was expecting something like a "Figure 1" caption after the plot, but do not get any. What should I do to get figure captions with an automatic numbering?