Modularising code

I’ve been working on a project where I’ve had to incorporate better development practices. One issue was the long-winded functions that required breaking up into into smaller pieces for unit testing, and easy digestion by future developers.

Background

• Working with non-programming but data/stat experts
• Long functions
• No testing

Example function

this_long_function <- function(data){
  
  data_tmp <-
    data %>% 
    dplyr::filter(this)
  
  data_tmp <-
    data_tmp %>%
    to_that
  
}

Issues: How do we easily understnad what each step is doing and further ensure they’re doing them correctly?

Modular code

#| eval = F
step1 <- function(data){
  do this
}

step2 <- function(data){
  do that
}

this_long_function <- function(data){
  
  data_tmp <-
    step1()
  
  data_tmp <-
    step2()
  
}

## Error: <text>:2:6: unexpected symbol
## 1: step1 <- function(data){
## 2:   do this
##         ^

test_that("add_rolling_year_data works", {

  zz =
    data.frame(year = 2022:2021,
               value = 2:1)

  result <- add_rolling_year_data(zz, 2)

  # Should have 2x 2022 with rolling values of 2022 and 2021
  # Should have 1 2021 with rolling values 2021
  expected =
    data.frame(year = c(2022,2021,2022),
               value = c(2L,1L,1L),
               year_rolling = c(2022L,2021L,2021L))

  expect_identical(result, expected = expected)


})

## Error in test_that("add_rolling_year_data works", {: could not find function "test_that"