---
title: "Lab 9: Strings and Regex"
---

```{r}
#| label: setup
#| include: false
knitr::opts_chunk$set(
  echo = TRUE,
  message = FALSE,
  warning = FALSE,
  fig.width = 6,
  fig.height = 3.6,
  fig.align = "center",
  dpi = 120,
  error = TRUE,
  fig.path = "_figs/lab-9-strings/"
)
library(tidyverse)
```

Build a quote from pieces, then write a few patterns.

Work in a **Quarto** document. Do **9.1** and **9.2** first. `words` comes with stringr.

```{r}
#| label: chunk-1
library(tidyverse)
```

---

## 1. Pieces and replacement

1. From `full <- "To be or not to be, that is the question."`, use `str_sub()` to pull two pieces and `str_c()` to join them so `writeLines()` prints a two-line quote.
2. Replace `"back"` and `"lack"` with `"foo"` in one call. Run it on `c("back", "lack")` and on `c("back", "lack", "black")`.

---

## 2. Regular expressions

Use `words`. For each item, print the matching words.

1. Four-letter words that start with `a`.
2. Words that start with a vowel.
3. Words that end in `ed` but not `eed`.
4. Words that start with three consonants.
5. Words that end in a consonant.
6. Words that end in `ing` or `ise`.
7. Words with two or more vowel-consonant pairs in a row (`[aeiou][^aeiou]` twice).