r - using .Last.value in rmarkdown/knitr -

having , rmd file below content:

```{r} data.frame(a=1) str(.last.value) ``` 

it renders data.frame rendering str(.last.value) produces ## null.
there knitr option or trick can use make works expected?
expected output second

## 'data.frame':    1 obs. of  1 variable: ##  $ a: num 1 

actually, there way make .last.value work.

```{r setup, include=false} knitr::opts_chunk$set(render = function(x, ...){     unlockbinding(".last.value", .basenamespaceenv)     assign(".last.value", x, .basenamespaceenv)     lockbinding(".last.value", .basenamespaceenv)     knitr::knit_print(x, ...) }) ``` 

this piece of code defines custom render function binds output .last.value.

though, above fix not prefect. behaviour little bit different console. example, in r console

> x <- 2 > .last.value [1] 2 

the .last.value returns last value if previous command nonvisible. on other hand, above hack knitr requires result printed.

```{r} x <- 2 x .last.value ``` 

---

update

to make .last.value works in r console, instead, consider following high-risk hack overwrites knitr internal function.

```{r setup, include=false} unlockbinding("knit_handlers", getnamespace("knitr")) evalq(   assign(     "knit_handlers",      function(fun, options) {       if (!is.function(fun)) fun = knit_print       if (length(formals(fun)) < 2)         stop("the chunk option 'render' must function of form ",              "function(x, options) or function(x, ...)")       merge_list(default_handlers, list(value = function(x, visible) {         unlockbinding(".last.value", .basenamespaceenv)         assign(".last.value", x, .basenamespaceenv)         lockbinding(".last.value", .basenamespaceenv)         if (visible) fun(x, options = options)       }))      }   ),    getnamespace("knitr") ) lockbinding("knit_handlers", getnamespace("knitr")) ``` 

this overwrites knitr internal function knit_handlers, subjects break @ anytime.