How to evaluate all chunks in Rmarkdown - r

Question

How do I evaluate all of the chunks in an Rmd document, without putting eval=TRUE at each chunk? The way I have it below, only the first chunk is evaluated.
```{r,eval=TRUE}
1+1
```
Some text
```
2+2
```
EDIT:
I'm trying to knit/compile to HTML.
```
require(knitr)
opts_chunk$set(eval = TRUE, tidy = TRUE, cache = FALSE, echo = FALSE, include = FALSE,
fig.path = 'figures/', dev = c("pdf"),
fig.width = 7, fig.height = 7)
```
some text
```
1+1
```
more text
```
2+2
```

Answer 1

eval=TRUE is the default behaviour for .Rmd chunks, so you shouldn't need to explicitly add it to your chunks' options.
However, you do need to include {r} after your opening fences in order for the chunk to be recognised as R code and evaluated accordingly. Chunks that do not open with ```{r} will not be run, hence the problem you're seeing.
A working example might be:
```{r}
1+1
```
Some text
```{r}
2+2
```
To insert a new, empty chunk with the appropriate fences and {r}, you can press Ctrl + Alt+i on Windows, or ⌘ + Option + i on Mac, or click this icon at the top right of the RStudio source pane (from memory, older versions of RStudio had an 'Insert' drop-down in that general area):

Answer 2

In your first chunk you can set knitr options globally.
opts_chunk$set(tidy = TRUE, cache = FALSE, echo = FALSE, include = FALSE,
fig.path = 'figures/', dev = c("pdf"),
fig.width = 7, fig.height = 7)
In any subsequent chunk, you can change these by the usual means but they only apply to that chunk.
EDIT. Here is a fuller example from K. Broman
```{r global_options, include=FALSE}
knitr::opts_chunk$set(fig.width=12, fig.height=8, fig.path='Figs/',
echo=FALSE, warning=FALSE, message=FALSE)
```