How to create individual chunks when using #+ with spin function in knitr R package -

when using #+ spin cannot separate chunks.

for example if r script 1 below:

#+

data(cars)

#+

cars

#+

plot(cars$speed, cars$dist)

i get:

```{r } data(cars)  ```{r } cars  ```{r } plot(cars$speed, cars$dist) ``` 

but not separate chunks, commands embedded in same chunk. how can separate chunks spin?