13: Intro to Strings/Regex

Author

Affiliation

Prof Amanda Luby

Carleton College
Stat 220 - Spring 2025

`babynames` intro

Replicate the “Amanda” plot with your own name using the starter code below. If your name doesn’t have enough data, try a friend or professor’s name

babynames %>%
  ___(name == ___ ) %>%
  ggplot(aes(x = ___, y = ___, col = ___)) +
  geom____()

Practice with `stringr`

Your turn

No code needed, just think about what it returns

Your turn 2

Fill in the blanks of the .Rmd file to…

Isolate the last letter of every name
and create a logical variable that displays whether the last letter is one of “a”, “e”, “i”, “o”, “u”, or “y”.
Use a weighted mean to calculate the proportion of children whose name ends in a vowel, by year (see ?weighted.mean).
and then display the results as a line plot.

babynames %>%
  mutate(last = ___, 
         vowel = ___) %>%
  group_by(___) %>%
  ___(p_vowel = weighted.mean(vowel, n)) %>%
  ___ +
  ___

Example: Carleton courses

The below code chunk imports a data set of the 6-credit courses offered at Carleton in Winter 2023. All three columns are character vectors.

courses <- read_csv("https://stat220-s25.github.io/data/winter2023_course_tbl.csv", col_types = list(course = col_character()))

(a)

How many of the course numbers end in .00? Use str_detect() or str_count() to help you answer this question.

Note that . is a special character in strings, so use \\. to get the literal period.

(b)

The section number appears after the decimal point. Use mutate() and str_sub() to create a section column containing this number.

(c)

How many courses contain the word Introduction? Does case matter here?

(d)

What is the longest course name (in terms of characters)? What is the shortest course name? Use str_length() to help you answer this question.

(e)

Use str_subset() to return the course names that contain exclamation points (!).

Practice with Regular Expressions

Your turn 1

Detect either “.” or “-” in the info vector.

a1 <- "Home: 507-645-5489"
a2 <- "Cell: 219.917.9871"
a3 <- "My work phone is 507-202-2332"
a4 <- "I don't have a phone"
info <- c(a1, a2, a3, a4)

Your turn: ends with a vowel

Fill in the code to determine how many baby names in 2015 ended with a vowel.

babynames %>% 
  ___(___ == ___) %>%                       # extract year 2015
  ___(ends_with_vowel = ___(___, ___)) %>%  # create logical column
  count(ends_with_vowel)                    # create a frequency table

Additional practice (if time)

A vector called words is loaded with stringr and contains a corpus of 980 words used in text analysis. Use stringr functions and regular expressions to find the words that satisfy the following descriptions.

1. Find all words that start with `y`.

pattern <- "type your pattern here"
str_subset(words, pattern)

character(0)

2. Find all words that end with `x`.

3. Find all words that are exactly three letters long.

4. Find all words that start with a vowel.

5. Find all words that start with consonants.

7. Find all words that end with `ing` or `ise`.

8. Find all words that have seven letters or more.

9. Find all words that start with three consonants.

--- title: "13: Intro to Strings/Regex" output: html_document --- ```{r setup, include=FALSE} knitr::opts_chunk$set(echo = TRUE) library(babynames) library(tidyverse) ``` # `babynames` intro Replicate the "Amanda" plot with your own name using the starter code below. If your name doesn't have enough data, try a friend or professor's name ```{r} #| eval: false babynames %>% ___(name == ___ ) %>% ggplot(aes(x = ___, y = ___, col = ___)) + geom____() ``` # Practice with `stringr` ## Your turn No code needed, just think about what it returns ## Your turn 2 Fill in the blanks of the .Rmd file to... 1. Isolate the last letter of every name 2. and create a logical variable that displays whether the last letter is one of "a", "e", "i", "o", "u", or "y". 3. Use a weighted mean to calculate the proportion of children whose name ends in a vowel, by year (see `?weighted.mean`). 4. and then display the results as a line plot. ```{r} #| eval: false # Remember to remove this line babynames %>% mutate(last = ___, vowel = ___) %>% group_by(___) %>% ___(p_vowel = weighted.mean(vowel, n)) %>% ___ + ___ ``` ## Example: Carleton courses The below code chunk imports a data set of the 6-credit courses offered at Carleton in Winter 2023. All three columns are character vectors. ```{r} courses <- read_csv("https://stat220-s25.github.io/data/winter2023_course_tbl.csv", col_types = list(course = col_character())) ``` ### (a) How many of the course numbers end in `.00`? Use `str_detect()` or `str_count()` to help you answer this question. Note that `.` is a special character in strings, so use `\\.` to get the literal period. ### (b) The section number appears after the decimal point. Use `mutate()` and `str_sub()` to create a `section` column containing this number. ### (c) How many courses contain the word `Introduction`? Does case matter here? ### (d) What is the longest course name (in terms of characters)? What is the shortest course name? Use `str_length()` to help you answer this question. ### (e) Use `str_subset()` to return the course names that contain exclamation points (`!`). # Practice with Regular Expressions ## Your turn 1 Detect either "." or "-" in the `info` vector. ```{r} a1 <- "Home: 507-645-5489" a2 <- "Cell: 219.917.9871" a3 <- "My work phone is 507-202-2332" a4 <- "I don't have a phone" info <- c(a1, a2, a3, a4) ``` ## Your turn: ends with a vowel Fill in the code to determine how many baby names in 2015 ended with a vowel. ```{r} #| eval: false # remember to remove this line babynames %>% ___(___ == ___) %>% # extract year 2015 ___(ends_with_vowel = ___(___, ___)) %>% # create logical column count(ends_with_vowel) # create a frequency table ``` ## Additional practice (if time) A vector called `words` is loaded with `stringr` and contains a corpus of 980 words used in text analysis. Use `stringr` functions and regular expressions to find the words that satisfy the following descriptions. #### 1. Find all words that start with `y`. ```{r} pattern <- "type your pattern here" str_subset(words, pattern) ``` #### 2. Find all words that end with `x`. #### 3. Find all words that are exactly three letters long. #### 4. Find all words that start with a vowel. #### 5. Find all words that start with consonants. #### 7. Find all words that end with `ing` or `ise`. #### 8. Find all words that have seven letters or more. #### 9. Find all words that start with three consonants.

babynames intro

Practice with stringr