R markdown, source and graphs

gr.R

ggplot(data = df, aes(x = x, y = y)) + geom_point()

test.Rmd

```{r data, echo=FALSE}
library("ggplot2")
library("knitr")
df  <- data.frame(x = rnorm(100), u = rnorm(100))
df$y  <- 1 + df$x + df$u
```


```{r test, echo=FALSE, results='asis'}
read_chunk('gr.R')
```

```{r test2, echo=FALSE, results='asis'}
source('gr.R')
```