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validate - asserts the following:

  • outcomes must have factor columns.

check - returns the following:

  • ok A logical. Does the check pass?

  • bad_classes A named list. The names are the names of problematic columns, and the values are the classes of the matching column.






An object to check.


validate_outcomes_are_factors() returns outcomes invisibly.

check_outcomes_are_factors() returns a named list of two components, ok and bad_classes.


The expected way to use this validation function is to supply it the $outcomes element of the result of a call to mold().


hardhat provides validation functions at two levels.

  • check_*(): check a condition, and return a list. The list always contains at least one element, ok, a logical that specifies if the check passed. Each check also has check specific elements in the returned list that can be used to construct meaningful error messages.

  • validate_*(): check a condition, and error if it does not pass. These functions call their corresponding check function, and then provide a default error message. If you, as a developer, want a different error message, then call the check_*() function yourself, and provide your own validation function.


# Not a factor column.
check_outcomes_are_factors(data.frame(x = 1))
#> $ok
#> [1] FALSE
#> $bad_classes
#> $bad_classes$x
#> [1] "numeric"

# All good
check_outcomes_are_factors(data.frame(x = factor(c("A", "B"))))
#> $ok
#> [1] TRUE
#> $bad_classes
#> list()