PA 8: The 12 Days of Christmas

Starter Functions

library(tidyverse)

Download starter .qmd file

Introduction

The song “12 Days of Christmas”, written around 1780, tells the tale of many gifts a person receives in the days leading up to Christmas (link to lyrics. You may want to listen to the song.

These gifts repeat and compound; on the first day, the narrator receives

A partridge in a pear tree.

On the twelfth day, they receive

Twelve Drummers Drumming
Eleven Pipers Piping
Ten Lords a Leaping
Nine Ladies Waiting
Eight Maids a Milking
Seven Swans a Swimming
Six Geese a Laying
Five Golden Rings
Four Calling Birds
Three French Hens
Two Turtle Doves
And a Partridge in a Pear Tree

This week, your task will be to write functions that automatically sing this very repetitive song. In the practice activity, we will start by writing two helper functions which we will use in the lab to write a function to sing this entire song.

Data set

Run the code provided to load in a data set called xmas that contains the crucial information about the gifts in the song. We will use this data set to test out our functions as we work on them.

xmas <- read.csv("https://github.com/earobinson95/stat331-calpoly/raw/master/practice-activities/data/xmas.csv") |> 
  janitor::clean_names()

Caution

Your functions can - and should! - reference each other. That is, don’t duplicate code; use earlier, smaller functions inside your larger functions.

Advice

Make smaller versions of the xmas data set (e.g., the first two days).
Once you feel confident in your function code, use the smaller version of the data to test the functions you write, before you test them on the full data set.
Don’t sweat the small stuff, we will build off of the practice activity and use iteration in the lab this week. Then you will have a chance to “polish” the song for Flex Points!

1 Plurals – `pluralize_gift()`

The gifts are listed in singular: for example, on day five the narrator receives “five golden rings”, but the entry in the data set for the gift on day five simply says “ring”.

Tip

Hint 1: The gifts on days six and nine have unusual pluralization. You may assume that in other data sets, there will be no additional special cases besides these types and that “moose” would become “meese”.

Hint 2: The following small examples may be useful to you:

my_names <- c("Kimberly", "Trini", "Jason", "Billy", "Zach", "Tommy")
str_c(my_names, "s", sep = "")

[1] "Kimberlys" "Trinis"    "Jasons"    "Billys"    "Zachs"     "Tommys"

str_replace(my_names, "y$", "ies")

[1] "Kimberlies" "Trini"      "Jason"      "Billies"    "Zach"      
[6] "Tommies"

Important!

You should absolutely not “hard-code” anything into this function; this function should work in general, not just for the items in The 12 Days of Christmas. For example, the word “rings” should not appear anywhere in the function. I should be able to give it any gift and get back the plural of that gift.

Using the skeleton of the pluralize_gift() function, complete the code so that the function takes a gift and returns the appropriate plural.

# Function that takes a noun and makes it plural
# Arguments -- gift -- A string or vector of strings
# Return -- A string or vector of strings with the pluralized words
# Hint -- the stringr functions will be incredibly handy here!

pluralize_gift <- function(gift){

  gift <- # your code to modify the gift here

  return(gift)

}

Test Your Function

Try your function out on the smaller and then larger gift data set. Consider: is your function vectorized? It does not have to be, but you can try it out if you want!

# Will work if your function is vectorized! 
pluralize_gift(gift = xmas$gift_item)

 [1] "partridge" "dove"      "hen"       "bird"      "ring"      "goose"    
 [7] "swan"      "maid"      "lady"      "lord"      "piper"     "drummer"

# Will work if your function is not vectorized!
map_chr(.x = xmas$gift_item, 
        .f = ~ pluralize_gift(gift = .x)
        )

 [1] "partridge" "dove"      "hen"       "bird"      "ring"      "goose"    
 [7] "swan"      "maid"      "lady"      "lord"      "piper"     "drummer"

2 Creating sentences – `make_phrase()`

Write a function called make_phrase() that takes as input the necessary information, and returns a phrase. For example,

make_phrase(day_num   = 4, 
            adjective = "calling",
            item      = "birds",  
            verb      = "",
            location  = "")

should return

"four calling birds"

and

make_phrase(day_num  = 10, 
            adjective = NA, 
            item      = "lords", 
            verb      = "a-leaping",
            location  = NA
            )

should return

"ten lords a-leaping"

Tip

The day_in_words variable isn’t quite what you want! For example, you want 12 to say "twelve" not "twelfth" or 12. I suggest using the english package!

make_phrase <- function(day_num, adjective, item, verb, location) {
  
  ## Step 1: Replace NAs with blank strings
  adjective <- str_replace_na(adjective, "")
  
  
  ## Step 2: If the day number is larger than 1, the gift items need pluralized!
  ### Hint: call the function you created above!
  
  
  ## Step 3: Figure out if a gift item starts with a vowel
  
  
  ## Step 4: For the first day, if the gift item starts with a vowel, add "an" to the beginning and if the gift item does not start with a vowel, add "a" to the beginning
  ### For example, "a partridge in a pear tree". Pretend you could have "an eagle in a pear tree". 
  ### If it is not the first day, use just the number word (e.g. "four golden rings" and "ten lords a-leaping")
  ### See tip above about how you will need to address number vs the number word (e.g. 10 vs ten vs tenth)
  
  
  ## Step 5: Glue all of the pieces together into one string and return!

}

Test Your Function

Try your function out on the xmas data, by making a new variable containing the daily phrases. Notice I’ve provided you with the code to iterate through each row of the data set to create a phrase – all you need to do is provide the necessary inputs into pmap_chr().

xmas_phrase <- xmas |> 
  mutate(full_phrase = pmap_chr(.l = list(day_num   = ______,
                                          adjective = ______, 
                                          item      = ______, 
                                          verb      = ______, 
                                          location  = ______
                                          ), 
                                .f = make_phrase
                                )
         )

Error: <text>:2:56: unexpected input
1: xmas_phrase <- xmas |> 
2:   mutate(full_phrase = pmap_chr(.l = list(day_num   = __
                                                          ^

Canvas Submission

Your full_phrase column is the answer to this week’s Practice Activity.

Copy and paste your full_phrase column to show me the phrases you made!

xmas_phrase |> 
  pull(full_phrase)

Error in eval(expr, envir, enclos): object 'xmas_phrase' not found

--- title: "PA 8: The 12 Days of Christmas" subtitle: "Starter Functions" format: html: embed-resources: true code-tools: true toc: true number-sections: true editor: source execute: error: true echo: true message: false warning: false --- ```{r setup} library(tidyverse) ``` [Download starter .qmd file](PA8-twelve-days-of-christmas.qmd) ## Introduction {-} The song *"12 Days of Christmas"*, written around 1780, tells the tale of many gifts a person receives in the days leading up to Christmas ([link to lyrics](https://en.wikipedia.org/wiki/The_Twelve_Days_of_Christmas_(song)). You may want to listen to the song. These gifts repeat and compound; on the first day, the narrator receives A partridge in a pear tree. On the twelfth day, they receive Twelve Drummers Drumming Eleven Pipers Piping Ten Lords a Leaping Nine Ladies Waiting Eight Maids a Milking Seven Swans a Swimming Six Geese a Laying Five Golden Rings Four Calling Birds Three French Hens Two Turtle Doves And a Partridge in a Pear Tree This week, your task will be to write functions that automatically sing this very repetitive song. In the practice activity, we will start by writing two helper functions which we will use in the lab to write a function to sing this entire song. ## Data set {-} Run the code provided to load in a data set called `xmas` that contains the crucial information about the gifts in the song. We will use this data set to test out our functions as we work on them. ```{r} xmas <- read.csv("https://github.com/earobinson95/stat331-calpoly/raw/master/practice-activities/data/xmas.csv") |> janitor::clean_names() ``` ::: callout-caution Your functions can - and should! - reference each other. That is, don't duplicate code; use earlier, smaller functions inside your larger functions. ::: ::: callout-tip ### Advice + Make smaller versions of the `xmas` data set (e.g., the first two days). + Once you feel confident in your function code, use the smaller version of the data to test the functions you write, *before* you test them on the full data set. + Don't sweat the small stuff, we will build off of the practice activity and use iteration in the lab this week. Then you will have a chance to "polish" the song for Flex Points! ::: ## Plurals -- `pluralize_gift()` The gifts are listed in singular: for example, on day five the narrator receives "five golden rings", but the entry in the data set for the gift on day five simply says "ring". ::: callout-tip *Hint 1:* The gifts on days six and nine have unusual pluralization. You may assume that in other data sets, there will be **no** additional special cases besides these types and that "moose" would become "meese". *Hint 2:* The following small examples may be useful to you: ```{r} my_names <- c("Kimberly", "Trini", "Jason", "Billy", "Zach", "Tommy") str_c(my_names, "s", sep = "") str_replace(my_names, "y$", "ies") ``` ::: ::: callout-caution #### Important! You should **absolutely not** "hard-code" anything into this function; this function should work in general, not just for the items in *The 12 Days of Christmas*. For example, the word "rings" should not appear anywhere in the function. I should be able to give it any gift and get back the plural of that gift. ::: Using the skeleton of the `pluralize_gift()` function, complete the code so that the function takes a gift and returns the appropriate plural. ```{r pluralize-function} # Function that takes a noun and makes it plural # Arguments -- gift -- A string or vector of strings # Return -- A string or vector of strings with the pluralized words # Hint -- the stringr functions will be incredibly handy here! pluralize_gift <- function(gift){ gift <- # your code to modify the gift here return(gift) } ``` ::: callout-warning ### Test Your Function Try your function out on the smaller and then larger gift data set. Consider: is your function *vectorized*? It does not have to be, but you can try it out if you want! ```{r pluralize-test} # Will work if your function is vectorized! pluralize_gift(gift = xmas$gift_item) # Will work if your function is not vectorized! map_chr(.x = xmas$gift_item, .f = ~ pluralize_gift(gift = .x) ) ``` ::: ## Creating sentences -- `make_phrase()` Write a function called `make_phrase()` that takes as input the necessary information, and returns a phrase. For example, make_phrase(day_num = 4, adjective = "calling", item = "birds", verb = "", location = "") should return "four calling birds" and make_phrase(day_num = 10, adjective = NA, item = "lords", verb = "a-leaping", location = NA ) should return "ten lords a-leaping" ::: callout-tip The `day_in_words` variable isn't quite what you want! For example, you want `12` to say `"twelve"` **not** `"twelfth"` or `12`. I suggest using the `english` package! ::: ```{r phrase-function} make_phrase <- function(day_num, adjective, item, verb, location) { ## Step 1: Replace NAs with blank strings adjective <- str_replace_na(adjective, "") ## Step 2: If the day number is larger than 1, the gift items need pluralized! ### Hint: call the function you created above! ## Step 3: Figure out if a gift item starts with a vowel ## Step 4: For the first day, if the gift item starts with a vowel, add "an" to the beginning and if the gift item does not start with a vowel, add "a" to the beginning ### For example, "a partridge in a pear tree". Pretend you could have "an eagle in a pear tree". ### If it is not the first day, use just the number word (e.g. "four golden rings" and "ten lords a-leaping") ### See tip above about how you will need to address number vs the number word (e.g. 10 vs ten vs tenth) ## Step 5: Glue all of the pieces together into one string and return! } ``` ::: callout-warning ### Test Your Function Try your function out on the `xmas` data, by making a new variable containing the daily phrases. Notice I've provided you with the code to iterate through each row of the data set to create a phrase -- all you need to do is provide the necessary inputs into `pmap_chr()`. ```{r} xmas_phrase <- xmas |> mutate(full_phrase = pmap_chr(.l = list(day_num = ______, adjective = ______, item = ______, verb = ______, location = ______ ), .f = make_phrase ) ) ``` ::: ::: callout-note ### Canvas Submission {-} > Your `full_phrase` column is the answer to this week's Practice Activity. > > Copy and paste your `full_phrase` column to show me the phrases you made! ```{r} xmas_phrase |> pull(full_phrase) ``` :::

Introduction

Data set

1 Plurals – pluralize_gift()

2 Creating sentences – make_phrase()

1 Plurals – `pluralize_gift()`

2 Creating sentences – `make_phrase()`