Lecture 07 — From Script to Report

Why Quarto? Code chunks, Markdown, and a professional Word document

Bill Perry

2026-09-10

Where we left off (Lectures 05–06)

Wrangling — filter(), select(), mutate(), arrange()
Descriptive stats — mean, median, SD, SE with group_by() + summarize()
Figures — boxplots and mean ± SE plots, saved as PNG (GGPlot I)
Everything so far lives in a .R script

Note

✅ Key idea from Lecture 06

You now have a complete descriptive analysis of the leaf data. Today we turn that pile of code into a report a human can read — before we even get to formal hypothesis testing.

Goals for today

Understand why a script alone is not enough
Meet Quarto — code and writing in one file
Learn the three ingredients:
- YAML front matter — the recipe at the top
- Markdown — formatted text, no clicking
- Code chunks — R that runs and shows its output
Render our leaf analysis to a professional Word document

Tip

🖐 Try it yourself

By the end you will click Render and get a finished Word report of our leaf study.

Tools today:

No new packages — just Positron + Quarto (built in)

References:

How to Use These Slides — Predict · Type · Render

This lecture runs in four short chunks. After each chunk you switch to the activity and build your own report.

For every snippet, do three things:

Predict — before you Render, say what the document will show
Type it out by hand — do not copy-paste
Render and compare to your prediction

Note

✅ Why bother? (the evidence)

Predicting first forces you to retrieve how Markdown and chunks behave. The surprise when you’re wrong is what makes it stick.
Typing by hand builds muscle memory for YAML indentation and chunk syntax — exactly where beginners slip.
Chunk → immediate practice keeps each new idea in working memory long enough to form a lasting schema.

🧩 Chunk 1 of 4 · Why Quarto?

We will cover: the pain of script-plus-copy-paste, literate programming, and reproducibility — the real payoff.

Tip

🖐 After this chunk: open the finished example t_test_report.qmd, Render it, then start Activity Step 1.

Part 1 · The problem with scripts

What happens after the analysis?

Your .R script is great for running code. But when the lab report is due you have to:

Run the script
Copy each number into Word by hand
Export every plot, then drag it in
Re-do all of it when the data changes

Warning

⚠️ Watch out!

Every hand-copied number is a chance for a typo. Change one data point and the whole report is out of date.

Note

📊 Coming from Excel?

This is the same pain as pasting a chart into Word, then editing the spreadsheet and forgetting to update the chart.

The idea: keep code and writing together

Literate programming — write the story and the code in the same file.

Your explanation sits next to the code that made it
The numbers and plots are computed, never copied
Press Render → a finished document appears

one .qmd file  →  Render  →  Word / HTML / PDF / PowerPoint

Note

📖 New word

Quarto = the tool that turns one plain-text .qmd file into a polished document.

Note

✅ Key idea

A script does the analysis.

A Quarto document does the analysis and explains it — and rebuilds itself on demand.

Reproducibility — the real payoff

Change your data file, press Render, and:

Every mean, SD, and p-value recalculates
Every figure redraws
Every sentence with a number updates itself

This is what scientists mean by reproducible — anyone (including future-you) can regenerate your exact results.

Tip

🖐 Try it yourself

Imagine a reviewer finds one bad leaf measurement. With Quarto the fix is: delete the row, then press Render — every table, figure, and sentence downstream updates to match.

Diagram of the pipe operator: leaf_df flows down into filter(shade == “sunny”), then flows down into summary(), read as “take leaf_df, then filter, then summarise.”

Note

Same philosophy as Lecture 02: never overwrite your raw numbers — let the document rebuild from them.

🛑 Pause — See It, Then Do Activity Step 1

🛑 Do Activity Step 1 now

Open t_test_report.qmd, press Render, and watch a script become a finished Word report. Then make your own new .qmd (Step 1).

🧩 Chunk 2 of 4 · Anatomy of a `.qmd`

We will cover: the three ingredients — YAML front matter, Markdown text, and named code chunks.

Tip

🖐 After this chunk: Activity Steps 2–4 (write the YAML, add Markdown, add named chunks).

Part 2 · Anatomy of a `.qmd` file

Three parts, top to bottom

Every Quarto document has the same three ingredients:

1. YAML front matter  ← the recipe (title, output type)
2. Markdown text      ← your writing, formatted
3. Code chunks        ← R that runs and shows results

You already read these every day — this whole lecture is a .qmd file.

Note

📖 New word

.qmd = a Quarto markdown file. Plain text you can open anywhere.

Note

✅ Key idea

If you can write a script and write an email, you already know two of the three parts. Only the YAML is new.

Ingredient 1 · YAML front matter

The block at the very top, fenced by three dashes ---. It is the recipe — what to build and how:

---
title: "Leaf Morphology Report"
author: "Your Name"
date: today
format: docx
---

title, author, date — appear at the top of the report
format: docx — make a Word document

Warning

⚠️ Watch out!

YAML is space-sensitive. Indent with spaces, never tabs. A stray space is the #1 beginner error.

Note

📖 New word

YAML = “YAML Ain’t Markup Language.” Just a tidy list of key: value settings.

format: is the only line you change to get Word vs. HTML vs. PowerPoint.

Ingredient 2 · Markdown text

Note

🔮 Predict first: Look at the Markdown block below. Before it renders, sketch what it becomes — which line is a big heading, which are bullets, what turns bold?

Markdown is formatting with symbols instead of toolbar buttons:

# A big heading
## A smaller heading

Normal text. Make it **bold** or *italic*.

- a bullet
- another bullet

[a link](https://r4ds.hadley.nz)

You write the symbols; Quarto turns them into real headings, bullets, and links.

Note

📖 New word

Markdown = a simple way to format plain text using a few symbols like #, *, and -.

Note

📊 Coming from Word?

**bold** is just the keyboard version of clicking the B button. Same result, no mouse.

Ingredient 3 · Code chunks

Note

🔮 Predict first: The chunk below runs mean(c(4, 3, 5, 7)). What number will land in the document? Predict before you look.

A code chunk is a fenced block of R that actually runs when you render:

```{r}
mean(c(4, 3, 5, 7))
```

Opening fence: ```{r} — the {r} means “this is R”
Closing fence: ```
The code and its output land in your document

Tip

Shortcut to insert a chunk: Ctrl/Cmd + Alt + I

Note

✅ Key idea

This is why we write code chunks: the result you see in the report is computed live, so it can never disagree with your code.

Name every chunk (just like your scripts)

Give each chunk a short label after r:

```{r load-data}
library(readxl)
leaf_df <- read_excel("data/2026_09_03_data_sci_leaf_area.xlsx")
```

If rendering fails, Quarto tells you which named chunk broke
Same habit as our small, named steps in Lectures 03–04

Warning

⚠️ Watch out!

Chunk labels must be unique — no two chunks named plot. Same rule as never overwriting a _plot object.

Note

✅ Key idea

Small, named chunks = easy to find the one line that failed. This is the same debugging strategy from your scripts.

Live Demo — Watch It Break (on purpose)

I’ll give two chunks the same label and Render:

```{r plot}
leaf_box_plot
```

… the same label again …

```{r plot}
leaf_mean_se_plot
```

Quarto stops:

ERROR: Duplicate chunk label 'plot'

The fix — make every label unique: plot-box and plot-mean-se.

Tip

✅ Why show a broken render?

Quarto names the exact problem — “Duplicate chunk label ‘plot’”. Once you know to read the error for the chunk name, you’ll go straight to the repeated label instead of guessing.

🛑 Pause — Do Activity Steps 2–4 Now

🛑 Do Activity Steps 2–4 now

Type the YAML by hand (spaces, not tabs), add a heading and bullets in Markdown, and create two uniquely named chunks. Predict what each renders before you press Render.

🧩 Chunk 3 of 4 · Chunk Options & Computed Values

We will cover: #| options to control what shows, and printing a computed table so the report always matches the data.

Tip

🖐 After this chunk: Activity Step 5 (compute a summary and print it into the report).

Chunk options — control what shows

Lines starting with #| are chunk options:

```{r leaf-plot}
#| echo: false      # hide the code, show the plot
#| fig-width: 6
# leaf_box_plot
```

Option	Effect
`echo: false`	hide the code, keep the output
`warning: false`	hide warning messages
`message: false`	hide package startup messages
`eval: false`	show code but do not run it

Note

✅ Key idea

For a clean report set echo: false — readers see the results, not the code. For a teaching handout, keep echo: true.

📖 R4DS §28.5 — Code chunks

Computed values — let the chunk print them

Note

🔮 Predict first: The chunk below builds a one-row-per-group summary. How many rows and columns will the printed table have?

Compute the numbers in a chunk and print the result — then refer to it in your prose:

```{r means}
#| echo: false
summary_df <- leaf_df |>
  group_by(shade) |>
  summarize(mean_mass = round(mean(mass_g, na.rm = TRUE), 3))
summary_df
```

Then, in the text:

Read the mean mass for each side from the mean_mass column of the table above.

The numbers are computed, never typed
Fix the data → press Render → the table fixes itself
No copy-paste, no stale numbers in your writing

Note

✅ Key idea

Keep every number your reader sees inside a chunk’s printed output (a table or a cat() line). Your prose then points at the results instead of restating them.

Warning

⚠️ Watch out!

The chunk that computes the value must run above the text that refers to it — Quarto renders top to bottom.

🛑 Pause — Do Activity Step 5 Now

🛑 Do Activity Step 5 now

Compute a group-means summary in a chunk and print it into the report. Predict the shape of the table before you Render.

🧩 Chunk 4 of 4 · Rendering to Word & Beyond

We will cover: YAML for a professional Word doc, one file → many outputs, and the render-often workflow.

Tip

🖐 After this chunk: Activity Steps 6–7 (make it professional; one file, three outputs).

Part 3 · Rendering to Word

One YAML block, a professional `.docx`

This front matter produces a clean, structured Word document:

---
title: "Leaf Morphology Report"
author: "Your Name"
date: today
format:
  docx:
    toc: true            # table of contents
    number-sections: true
    fig-width: 6
    fig-height: 4
---

Then press Render (or Ctrl/Cmd + Shift + K).

Note

✅ Key idea

toc: true and number-sections: true are what make it look like a report, not a printout.

Tip

🖐 Try it yourself

The activity gives you a ready-made template with exactly this front matter. You just add your writing and render.

📖 R4DS Ch 29 — Quarto formats

Same file, many outputs

The best part: one .qmd, many documents. Just list formats:

format:
  docx: default     # Word report
  html: default     # web page
  pptx: default     # PowerPoint

Hand in the Word file
Post the HTML to a site
Present the PowerPoint in lab

All from the same analysis — no re-doing anything.

Note

✅ Key idea

This is exactly how these lecture slides are built. One file → slides, Word, and PowerPoint.

The render workflow

Every time, it is the same three moves:

Write — add Markdown text and named code chunks
Render — Ctrl/Cmd + Shift + K
Read the output; fix the named chunk if it errors

Quarto runs your code top to bottom in a fresh session — so the order of your chunks matters.

Warning

⚠️ Watch out!

If it renders differently than the console, it is almost always chunk order: load libraries and data first.

Tip

Render often — after every few chunks — so a break is easy to trace. Same as running your script line by line.

🛑 Pause — Do Activity Steps 6–7 Now

🛑 Do Activity Steps 6–7 now

Upgrade the YAML for a TOC and numbered sections, copy in the template’s table and figure, then render to Word, HTML, and PowerPoint.

Wrap-up · What you can now do

Explain why a Quarto report beats a bare script
Recognize the three parts: YAML, Markdown, code chunks
Write and name a code chunk, set echo/warning options
Compute values in a chunk and print them so the report always matches the data
Set up YAML to render a professional Word document
Render one file to Word, HTML, and PowerPoint

Tip

🖐 Before next class

Open the activity template, drop in your Lecture 06 summary statistics, and render it to Word.

Note

✅ Key idea

You turned a script into a reproducible report. From here on, every analysis can be a document that rebuilds itself — including the t-test you’ll run in Lecture 09.

Up next — Lecture 08 (Flex/Catch-up), then Lecture 09:

The two-sample t-test — formally testing our leaf hypothesis
…written up in your new Quarto report!

Getting unstuck

When Render breaks (it will — that is normal):

Read which named chunk failed — it is in the message
Did you load library(...) and the data in a chunk above?
Check the YAML: spaces not tabs, --- on its own line
Is every chunk label unique?
Render often so the break is easy to find

Note

✅ Key idea

A Quarto error names the chunk. That is a gift — go straight to that block.

Note

📊 Reference

The Quarto guide is excellent and searchable: quarto.org/docs/guide

Lecture 07 — From Script to Report

Where we left off (Lectures 05–06)

Goals for today

How to Use These Slides — Predict · Type · Render

🧩 Chunk 1 of 4 · Why Quarto?

Part 1 · The problem with scripts

What happens after the analysis?

The idea: keep code and writing together

Reproducibility — the real payoff

🛑 Pause — See It, Then Do Activity Step 1

🧩 Chunk 2 of 4 · Anatomy of a .qmd

Part 2 · Anatomy of a .qmd file

Three parts, top to bottom

Ingredient 1 · YAML front matter

Ingredient 2 · Markdown text

Ingredient 3 · Code chunks

Name every chunk (just like your scripts)

Live Demo — Watch It Break (on purpose)

🛑 Pause — Do Activity Steps 2–4 Now

🧩 Chunk 3 of 4 · Chunk Options & Computed Values

Chunk options — control what shows

Computed values — let the chunk print them

🛑 Pause — Do Activity Step 5 Now

🧩 Chunk 4 of 4 · Rendering to Word & Beyond

Part 3 · Rendering to Word

One YAML block, a professional .docx

Same file, many outputs

The render workflow

🛑 Pause — Do Activity Steps 6–7 Now

Wrap-up · What you can now do

Getting unstuck

🧩 Chunk 2 of 4 · Anatomy of a `.qmd`

Part 2 · Anatomy of a `.qmd` file

One YAML block, a professional `.docx`