Glossary

For more context on why this particular SCT is a good idea, you can consult the Guides. None of the examples below specify any custom messages; you can consult the function documentation to figure out how you can override the automatically generated messages.

Check object

# solution
x <- 10

# sct
ex() %>% check_object("x") %>% check_equal()

# solution
x <- data.frame(a = 1:3, b = 4:6)

# sct
ex() %>% check_object("x") %>% {
  check_column(., "a") %>% check_equal()
  check_column(., "b") %>% check_equal()
}

Check function call

# solution
mean(1:10, na.rm = TRUE)

# sct
ex() %>% check_function("mean") %>% {
  check_arg(., "x") %>% check_equal()
  check_arg(., "na.rm") %>% check_equal()
}

Check function result

# solution
class(TRUE)

# sct
ex() %>% check_function("class") %>% check_result() %>% check_equal()

Check object created through function call

# solution
x <- mean(1:10, na.rm = TRUE)

# sct
ex() %>% check_correct(
  check_object(., "x") %>% check_equal(),
  check_function(., "mean") %>% {
    check_arg(., "x") %>% check_equal()
    check_arg(., "na.rm") %>% check_equal()
  }
)

Check output

# solution
print(mtcars)

# sct
ex() %>% check_output_expr("mtcars")

# solution
print("Hi, DataCamp")

# sct
# robust against capitalization, multiple spaces and different names
ex() %>% check_output("[H|h]i,\\s+[a-zA-Z]+?")

Check if else

# solution
x <- TRUE
if (x) {
  print("a")
} else {
  print("b")
}

# sct
ex() %>% check_if_else() %>% {
  check_cond(.) %>% check_code("x")
  check_if(.) %>% check_function("print") %>% check_arg("x") %>% check_equal()
  check_else(.) %>% check_function("print") %>% check_arg("x") %>% check_equal()
}

Check for loop

# solution
for (i in 1:10) {
  print(i)
}

# sct
ex() %>% check_for() %>% {
  check_cond(.) %>% check_code("in\\s*1:10")
  check_body(.) %>% check_function("print") %>% check_arg("x") %>% check_equal(eval = FALSE)
}

Check function definition

# solution
my_fun <- function(a, b) {
    abs(a) + abs(b)
}

# sct
ex() %>% check_fun_def("my_fun") %>% {
  check_arguments(.)
  check_call(., 1, 2) %>% check_result() %>% check_equal()
  check_call(., -1, 2) %>% check_result() %>% check_equal()
  check_body(.) %>% {
    check_function(., "abs", index = 1)
    check_function(., "abs", index = 2)
  }
}

Check library or require call

# solution
library(dplyr)

# sct
ex() %>% check_library("dplyr")

Check through string matching

# solution
"R is Rsome!"

# sct
# robust against capitalization and multiple spaces
ex() %>% check_code("^\"[r|R] is [r|R]some!?\"$")

Check ggplot

# solution
library(ggplot2)
ggplot(mtcars, aes(wt, hp)) +
  geom_point()

# sct
ex() %>% {
  check_function(., "ggplot") %>% check_arg("data") %>% check_equal()
  check_function(., "aes") %>% {
    check_arg(., "x") %>% check_equal(eval = FALSE) 
    check_arg(., "y") %>% check_equal(eval = FALSE)
  }
  check_function(., "geom_point")
}

NOTE: These exercises are pulled from a DataCamp course. You can find the source here.