Create appendix with R-code in rmarkdown/knitr

Question

Is it possible to get all of the code in a appendix. Say I have two chunks in a document and then some text.

```{r, echo=TRUE}
x <- 4+5
x
```  
Above is X out         


        

Answer 1

Another possibility:

### Appendix 
```{r, ref.label=knitr::all_labels(),echo=TRUE,eval=FALSE}
```

as suggested by Yihui's nice example