Importing matplotlib with reticulate in R

I was able to get things working by changing the R Markdown code block to read:

```{r}
library(reticulate)
use_python('/usr/bin/python3')
```

```{python}
import matplotlib.pyplot as plt
```

I still don't really understand why, but it seems that reticulate doesn't play nice with anaconda installations. Maybe it has something to do with anaconda being set up to work well with an interactive Jupyter notebook.