In emptyfield-ds/r_packages_write_code: Tools for the Avalanche Data Science Team

Your Turn 1

1. Re-write this ggplot2 theme as a function. Call it theme_avalanche_h().

library(ggplot2)

theme_minimal(base_size = 14) + 
  theme(panel.grid.minor = element_blank(), panel.grid.major.y = element_blank())

1. Run this code to test that your function works

residents_per_sector <- 
  data.frame(
    sector = as.factor(1:8),
    residents = c(1000, 2034, 4594, 2304, 8093, 1200, 300, 2398)
  )

ggplot(residents_per_sector, aes(forcats::fct_reorder(sector, residents), residents)) +
  geom_col() + 
  coord_flip() + 
  xlab("sector") + 
  theme_avalanche_h()

Your Turn 2

1. Create a new file with use_r() called "db_con"
2. Put this function in the file and save it:

db_con <- function(dbname = "residents_per_sector") {
  dbname <- match.arg(dbname)
  # We'll pretend we've connected to a database
  # and just return some hard-coded data instead.
  data.frame(
    sector = as.factor(1:8),
    residents = c(1000, 2034, 4594, 2304, 8093, 1200, 300, 2398)
  )
}

1. Use load_all() to load the package function.
2. Run this code to make sure it works:

ggplot(
  db_con(), 
  aes(forcats::fct_reorder(sector, residents), residents)
) +
  geom_col() + 
  coord_flip() + 
  xlab("sector") 

Your Turn 3

1. Fix the code in R/themes.R to use ggplot2:: instead of library(ggplot2)
2. Run use_package("ggplot2") to add ggplot2 to Imports
3. Re-load the package (Cmd/Ctrl+Shift+L) and run this code to make sure it works:

ggplot(
  db_con(), 
  aes(forcats::fct_reorder(sector, residents), residents)
) +
  geom_col() + 
  coord_flip() + 
  xlab("sector") +
  theme_avalanche()

Your Turn 4

1. We need roxygen2 for this exercise. We'll learn more about it in the next module. For now, just run use_roxygen_md()
2. Run use_tibble() and use_data_table()
3. In R/get_data.R, edit the function to be able to return a data table: Add the argument data_table = FALSE. If data_table is TRUE, convert the data frame with data.table::as.data.table()
4. Load the package and run this code to make sure it works:

res_data <- get_resident_data(data_table = TRUE)

stopifnot(data.table::is.data.table(res_data))

res_data

---

Finish early? Try this stretch goal:

Run use_pipe() to add the magrittr pipe to your package. What changed?

Take-aways

• Add R files with use_r(); load the functions with load_all(); build the package with build()
• Import packages with use_package() and use the format pkg::fun() to call functions from other packages
• usethis has several functions for setting up common or complicated packages that you might want to include, such as tibbles and data tables, the pipe, or Rcpp and friends.

emptyfield-ds/r_packages_write_code documentation built on Jan. 2, 2022, 12:15 a.m.