# Chunk Options

I've mostly followed [Knitr](http://yihui.name/knitr/options)'s naming for chunk options, but not all options are implemented.

Options are separated using ";" and need to be valid Julia expressions. Example: markdown code chunk that saves and displays a 12 cm wide image and hides the source code:

`julia; out_width="12cm"; echo=false`

Weave currently supports the following chunk options with the following defaults:


## Options for Code

- `echo = true`: Echo the code in the output document. If `false` the source code will be hidden.
- `results = "markup"`: The output format of the printed results. `"markup"` for literal block, `"hidden"` for hidden results, or anything else for raw output (I tend to use `"tex"` for Latex and `"rst"` for rest). Raw output is useful if you want to e.g. create tables from code chunks.
- `eval = true`: Evaluate the code chunk. If `false` the chunk won’t be executed.
- `term = false`: If `true` the output emulates a REPL session. Otherwise only stdout and figures will be included in output.
- `label = nothing`: Chunk label, will be used for figure labels in Latex as `fig:label`.
- `wrap = true`: Wrap long lines from output.
- `line_width = 75`: Line width for wrapped lines.
- `cache = false`: Cache results, depending on `cache` parameter on `weave` function.
- `hold = false`: Hold all results until the end of the chunk.
- `tangle = true`: Set tangle to `false` to exclude chunk from tangled code.


## Options for Figures

- `fig_width = 6`: Figure width passed to plotting library.
- `fig_height = 4`: Figure height passed to plotting library.
- `out_width`: Width of saved figure in output markup e.g. `"50%"`, `"12cm"`, `0.5\linewidth`
- `out_height`: Height of saved figure in output markup
- `dpi = 96`: Resolution of saved figures.
- `fig_cap`: Figure caption.
- `label`: Chunk label, will be used for figure labels in Latex as fig:label
- `fig_ext`: File extension (format) of saved figures.
- `fig_pos = "!h"`: Figure position in Latex, e.g.: `"ht"`.
- `fig_env = "figure"`: Figure environment in Latex.


## Set Default Chunk Options

You can set the default chunk options (and `weave` arguments) for a document using `weave_options` key in YAML [Header Configuration](@ref).
E.g. to set the default `out_width` of all figures you can use:

```yaml
---
weave_options:
  out_width : 50%
---
```

You can also set or change the default chunk options for a document either before weave using the `set_chunk_defaults` function.

```@docs
set_chunk_defaults!
get_chunk_defaults
restore_chunk_defaults!
```