Chunk level format options?

[shabbychef]

Hi,
I think in quarto I can set default options in the header YAML via something like:

format:
  html:
    out-width: "625px"
    out-height: "402px"
    fig-format: png
    fig-width: 10.0
    fig-height: 6.43
  pdf:
    fig-width: 11.5
    fig-height: 6.8

Is it possible to override these in a chunk in a way that is by output type? It seems that I can only override these options absolutely, and not conditionally on the output type.

thanks,

[shabbychef]

Also, TBH, it does not seem like the above actually works to set the default options...

[cderv]

Options you can set in YAML for each format and we document that in the references

• https://quarto.org/docs/reference/formats/html.html
• https://quarto.org/docs/reference/formats/pdf.html

Then you can modify some options at the chunk level. We also document that in the reference page for the computation engine used.
See for example knitr: https://quarto.org/docs/reference/cells/cells-knitr.html#figures

If you are using RStudio IDE or VS CODE, you should have YAML validation that helps you know what you can set where.

[shabbychef]

I don't know how YAML validation is supposed to work, but I do know that the following chunk options do not compile under quarto:

```{r 'plot_foo'}
#| html: out-width: "625px"
#| html: out-height: "402px"
#| pdf: out-width: "\\textwidth"
#| pdf: out-height: "0.64\textwidth"

[cderv]

Oh I understand now what you mean by "conditionally on the output type". Sorry I missed that.

There is no Quarto-way yet to make that happens.

Currently, conditional content are on the block levels using fenced div with special classes - see https://quarto.org/docs/authoring/conditional.html#content-visible

You would would need to use this feature and reuse the code chunk (https://bookdown.org/yihui/rmarkdown-cookbook/reuse-chunks.html) while changing the options

```{r}
#| labels: main-plot
#| include: false
plot(mtcars)
```

::: {.content-visible when-format="html"}
```{r}
#| ref.label: main-plot
#| out-width: 625px
```
:::

::: {.content-visible when-format="pdf"}
```{r}
#| ref.label: main-plot
#| out-width: "100%"
```
:::

With knitr, one could use conditional in chunk options too - Example:

```{r}
#| include: false
units <- function() {
  if (knitr::is_html_output()) {
    "625px"
  } else if (knitr::is_latex_output()) {
    "100%"
  }
}
```

```{r}
#| label: main-plot
#| out-width: !expr units()
plot(mtcars)
```

It is not that straightforward, and maybe we can come with a better API for that, directly in YAML. 🤔

[shabbychef]

I can confirm that the following does not raise an error (but it appears to have no effect on the output):

```{r 'plot_foo'}
#| format:
#|   html: 
#|     out-width: "625px"
#|     out-height: "402px"
#|   pdf: 
#|     out-width: "50%"
#|     out-height: "50%"

So perhaps this syntax could be used in the future...

[cderv]

I have added your suggestion to the issue: #2416