---
title: "One file, two formats"
subtitle: "Quarto parameters, interactive HTML and PowerPoint"
format:
  html:
    embed-resources: true
---

## Start here

**Goal:** write one Quarto file, render HTML and PowerPoint, and switch a plot on or off.

A **parameter** is a named setting you choose when rendering. Here, `show_plot` controls whether a plot appears.

You need Quarto, R, and the R packages **knitr**, **rmarkdown**, and **plotly** installed. The plot uses R's built-in `cars` dataset.

If needed, install the packages once in the **R console**, before rendering:

```r
install.packages(c("knitr", "rmarkdown", "plotly"))
```

In Positron, create a plain text file named **`my-report.qmd`**. Use the Source editor to enter the code in steps 1 and 2.

## 1. Add the header

Put this at the very top of `my-report.qmd`, including both `---` lines:

```yaml
---
title: "My first parameterized report"
format:
  html:
    embed-resources: true
  pptx: default
params:
  show_plot: true
execute:
  echo: false
---
```

Keep the indentation. `true` shows the plot; `false` hides it. Embedded resources make the HTML easy to share as one file.

## 2. Add the content

Below the header, add this text and R chunk, including the backticks:

````markdown
## My plot

Stopping distance and speed from R's cars dataset.

```{{r}}
if (params$show_plot) {
  if (knitr::is_html_output()) {
    p <- plotly::plot_ly(cars, x = ~speed, y = ~dist,
                         type = "scatter", mode = "markers")
    plotly::layout(p,
                   xaxis = list(title = "Speed (mph)"),
                   yaxis = list(title = "Stopping distance (ft)"))
  } else {
    plot(cars$speed, cars$dist,
         xlab = "Speed (mph)",
         ylab = "Stopping distance (ft)",
         pch = 19)
  }
}
```
````

`params$show_plot` reads the setting. `if (...)` runs the plotting code only when it is true. `echo: false` hides the code in the output.

`knitr::is_html_output()` checks the output format. For HTML, it creates an interactive **Plotly** plot. For PowerPoint, the `else` branch draws the same data with R's `plot()`, which Quarto inserts as a static image.

## 3. Render both formats

Save the file. Open Positron's **Terminal** in the folder containing `my-report.qmd` and run these commands one at a time:

```bash
quarto render my-report.qmd --to html
quarto render my-report.qmd --to pptx
```

Open **`my-report.html`** in a browser: hover over points to see their values and drag to zoom. Double-click the plot to reset the view.

Open **`my-report.pptx`** in PowerPoint: the plot is a regular image, with no hover or zoom controls.

The same `##` heading becomes a section in HTML and a slide heading in PowerPoint. Run these commands in the Terminal, not the R console.

## 4. Hide the plot

In the header, change `show_plot: true` to **`show_plot: false`**. Save and rerun both commands. Reopen the outputs: the text stays, but the plot disappears.

You can also override the setting for one render without editing the file:

```bash
quarto render my-report.qmd --to html -P show_plot:true
quarto render my-report.qmd --to pptx -P show_plot:true
```

These commands bring the plot back, even with `false` saved in the header. Each render replaces the corresponding output file.

**Done when:** you have opened both formats and seen each with and without the plot.

## Keep handy

- Define the setting under `params:` in the header.
- Read it in R with `params$show_plot`.
- Choose the format with `--to html` or `--to pptx`.
- Use `knitr::is_html_output()` to choose an interactive or static plot.
- Override the setting with `-P show_plot:false`.

References: [Quarto's parameter guide](https://quarto.org/docs/computations/parameters.html) and [Plotly scatter plots](https://plotly.com/r/line-and-scatter/).