How can I create an Rmd template which allows appealing plotly output for DOCX and HTML?

Question

Running the below Rmd will return nice HTML output. However, when rendering a DOCX the resolution of the plot is not appealing. Increasing the dpi (e.g. to 600) makes the font sizes in the DOCX too small and blows up the HTML. The HTML can be fixed by adjusting fig.width and fig.height but the font size issue in the DOCX remains. I've been playing around for a while now and am struggling to find a generic solution that works for both outputs.

I'd like to be able to make both work "out-of-the-box". What can I do?

---
output: 
  rmarkdown::html_document:
    toc: false
  rmarkdown::word_document:
    toc: false
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = FALSE, fig.topcaption = FALSE,
                      warning = FALSE, message = FALSE, dpi = 100)

library(ggplot2) # 3.4.2
library(plotly) # 4.10.4
```

```{r myplot}
ggp <- ggplot(data = iris, aes(x = Sepal.Length)) +
  geom_histogram(binwidth = 4, fill = "forestgreen",
                 color = "white", alpha = 0.5) +
  theme_classic()

ggplotly(ggp)
```

Answer 1

The observed behaviour is related to how HTML widgets are handled during rendering of rmarkdown files to DOCX. A screenshot is taken via webshot and and included into the DOCX. The quality of the image is controlled via the webshot zoom parameter, which by default is 1. This returns images with a somewhat bad resolution.

The default zoom setting can be overwritten in the chunk options via e.g. screenshot.opts = list(zoom = 5).

For the example shown in the question the solution looks like this:

---
output: 
  rmarkdown::word_document:
    toc: false
  rmarkdown::html_document:
    toc: false
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = FALSE, fig.topcaption = FALSE,
                      warning = FALSE, message = FALSE, dpi = 100,
                      # adjust zoom here
                      screenshot.opts = list(zoom = 5))

library(ggplot2) # 3.4.2
library(plotly) # 4.10.4
```

```{r myplot}
ggp <- ggplot(data = iris, aes(x = Sepal.Length)) +
  geom_histogram(binwidth = 4, fill = "forestgreen",
                 color = "white", alpha = 0.5) +
  theme_classic()

ggplotly(ggp)
```

This is documented in the HTML widgets chapter in "bookdown: Authoring Books and Technical Documents with R Markdown".

Answer 2

I think I would add in a conditional statement that only runs the ggplotly if the output is html.

try adding this in the last chunk:

if(knitr::is_html_output()){
  plotly::ggplotly(ggp)
} else {
  ggp
}