Description Usage Arguments Examples

Provide facilities for checking the layout of formulas. Use these
with an input that is the *value* of a formula, that is, with a V binding rather
than an EX binding.

1 2 3 4 5 6 7 8 9 | ```
formula_equals(F, target)
two_sided(F)
lhs_equals(F, ...)
rhs_equals(F, ...)
rhs_contains(F, ...)
``` |

`F` |
a formula from a student submission. |

`target` |
the desired attributes of the formula |

`...` |
expressions for the permissible parts of the formula |

1 2 3 4 5 6 7 8 9 10 11 | ```
CODE <- for_checkr(quote({
data(mtcars, package = "datasets")
mod <- lm(mpg ~ hp * wt + cyl, data = mtcars)
}))
fa <- formula_arg(line_calling(CODE, lm),
failif(! two_sided(V), "Modeling formulas should have two sides."),
failif(! lhs_equals(V, mpg), "The response variable should be mileage."))
# or, another style for the same thing ...
check(formula_arg(line_calling(CODE, lm)),
failif(! two_sided(V), "Modeling formulas should have two sides."),
failif(! lhs_equals(V, mpg), "The response variable should be mileage."))
``` |

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