Generate a message describing the first instance of a code mismatch. Three
functions are provided for working with code feedback: code_feedback() does
the comparison and returns a character description of the mismatch, or a
NULL if no differences are found. maybe_code_feedback() is designed to be
used inside fail() and related graded() messages, as in
"{maybe_code_feedback()}". And give_code_feedback() gives you a way to
add code feedback to any fail() message in a grade_this() or
grade_result() checking function.
code_feedback( user_code = .user_code, solution_code = .solution_code, env = .envir_prep, ..., allow_partial_matching = getOption("gradethis.allow_partial_matching", TRUE) ) maybe_code_feedback( user_code = get0(".user_code", parent.frame()), solution_code = get0(".solution_code", parent.frame()), env = get0(".envir_prep", parent.frame(), ifnotfound = parent.frame()), ..., allow_partial_matching = getOption("gradethis.allow_partial_matching", TRUE), default = "", before = getOption("gradethis.maybe_code_feedback.before", " "), after = getOption("gradethis.maybe_code_feedback.after", NULL), space_before = deprecated(), space_after = deprecated() ) give_code_feedback( expr, ..., env = parent.frame(), location = c("after", "before") )
| user_code, solution_code | String containing user or solution code. For
ease of use in |
|---|---|
| env | Environment used to standardise formals of the user and solution
code. Defaults to retrieving |
| ... | Ignored in |
| allow_partial_matching | A logical. If |
| default | Default value to return if no code feedback is found or code feedback can be provided. |
| before, after | Strings to be added before or after the code feedback message to ensure the message is properly formatted in your feedback. |
| space_before, space_after | Deprecated. Use |
| expr | A grading function — like |
| location | Should the code feedback message be added before or after? |
code_feedback() returns a character value describing the difference
between the student's submitted code and the solution. If no
discrepancies are found, code_feedback() returns NULL.
maybe_code_feedback() always returns a string for safe use in glue
strings. If no discrepancies are found, it returns an empty string.
give_code_feedback() catches fail() grades and adds code feedback to
the feedback message using maybe_code_feedback().
code_feedback: Determine code feedback by comparing the user's
code to the solution.
maybe_code_feedback: Return code_feedback() result when possible.
Useful when setting default fail() glue messages. For example, if there
is no solution, no code feedback will be given.
give_code_feedback: Appends maybe_code_feedback() to the
message generated by incorrect grades.
There are many different ways that code can be different, yet still the same. Here is how we detect code differences:
Validate the user code can be standardised via
rlang::call_standardise(). The env parameter is important for this
step as gradethis does not readily know about user defined
functions. Ex: read.csv("file.csv") turns into
read.csv(file = "file.csv")
If multiple formals are matched. Ex: read.csv(f = "file.csv") has f
match to file and fill.
Verify that every named argument in the solution appears in the user
code. Ex: If the solution is read.csv("file.csv", header = TRUE),
header must exist.
Verify that the user did not supply extra named arguments to ....
Ex: mean(x = 1:10, na.rm = TRUE) vs mean(x = 1:10)
Verify that every named argument in the solution matches the value of the
corresponding user argument. Ex: read.csv("file.csv", header = TRUE)
vs read.csv("file.csv", header = FALSE)
Verify that the remaining arguments of the user and solution code match
in order and value. Ex: mean(1:10, 0.1) vs mean(1:10, 0.2)
# code_feedback() ------------------------------------------------------ # Values are same, so no differences found code_feedback("log(2)", "log(2)")#> NULL# Functions are different code_feedback("log(2)", "sqrt(2)")#> I expected you to call `sqrt()` where you called `log()`.# Standardise argument names (no differences) code_feedback("read.csv('file.csv')", "read.csv(file = 'file.csv')")#> NULL# Partial matching is not allowed code_feedback("read.csv(f = 'file.csv')", "read.csv(file = 'file.csv')")#> `read.csv()` accepts more than one argument name that begins with `f`. As a result, R cannot figure out which argument you want to pass `"file.csv"` to. Check how you spelled `f`, or write out the full argument name.# Feedback will spot differences in argument values... code_feedback( "read.csv('file.csv', header = FALSE)", "read.csv('file.csv', header = TRUE)" )#> In `read.csv("file.csv", header = FALSE)`, I expected `header = TRUE` where you wrote `header = FALSE`.# ...or when arguments are expected to appear in a call... code_feedback("mean(1:10)", "mean(1:10, na.rm = TRUE)")#> Your call to `mean()` should include `"na.rm"` as one of its arguments. You may have misspelled an argument name, or left out an important argument.# ...even when the expected argument matches the function's default value code_feedback("read.csv('file.csv')", "read.csv('file.csv', header = TRUE)")#> Your call to `read.csv()` should include `"header"` as one of its arguments. You may have misspelled an argument name, or left out an important argument.# Unstandardised arguments will match by order and value code_feedback("mean(1:10, 0.1)", "mean(1:10, 0.2)")#> In `mean(1:10, 0.1)`, I expected `0.2` where you wrote `0.1`.# give_code_feedback() ------------------------------------------------- # We'll use this example of an incorrect exercise submission throughout submission_wrong <- mock_this_exercise( .user_code = "log(4)", .solution_code = "sqrt(4)" ) # To add feedback to *any* incorrect grade, # wrap the entire `grade_this()` call in `give_code_feedback()`: grader <- # ```{r example-check} give_code_feedback(grade_this({ pass_if_equal(.solution, "Good job!") if (.result < 2) { fail("Too low!") } fail() })) # ``` grader(submission_wrong)#>#> <gradethis_graded: [Incorrect] #> Too low! I expected you to call `sqrt()` where you called `log()`. #> ># Or you can wrap the message of any fail() directly: grader <- # ```{r example-check} grade_this({ pass_if_equal(.solution, "Good job!") if (.result < 2) { fail(give_code_feedback("Too low!")) } fail() }) # ``` grader(submission_wrong)#> <gradethis_graded: [Incorrect] #> Too low! I expected you to call `sqrt()` where you called `log()`. #> ># Typically, grade_result() doesn't include code feedback grader <- # ```{r example-check} grade_result( fail_if(~ round(.result, 0) != 2, "Not quite!") ) # ``` grader(submission_wrong)#> <gradethis_graded: [Incorrect] #> Not quite! Try it again. I have a good feeling about this. #> ># But you can use give_code_feedback() to append code feedback grader <- # ```{r example-check} give_code_feedback(grade_result( fail_if(~ round(.result, 0) != 2, "Not quite!") )) # ``` grader(submission_wrong)#> <gradethis_graded: [Incorrect] #> Not quite! Don't give up now, try it one more time. I expected you #> to call `sqrt()` where you called `log()`. #> ># The default `grade_this_code()` `incorrect` message always adds code feedback, # so be sure to remove \"{maybe_code_feedback()}\" from the incorrect message grader <- # ```{r example-check} give_code_feedback(grade_this_code(incorrect = "{random_encouragement()}")) # ``` grader(submission_wrong)#> <gradethis_graded_this_code: [Incorrect] #> But no need to fret, try it again. I expected you to call `sqrt()` #> where you called `log()`. #> >