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This small helper function allows to combine multiple formula() objects into one. In the case of duplicate variable entries, only the unique ones are used.

Usage

combine_formulas(..., combine = "both", env = parent.frame())

Arguments

...

Any number formula objects in "LHS ~ RHS" format, also supporting character strings.

combine

character on whether LHS and RHS duplicates are to be removed. Can be set to either "lhs", "rhs" or "both" (Default).

env

A new environment of the formula (def=parent.frame()).

Value

A formula as cbind(lhs_1, lhs_2, ...) ~ rhs_1 + rhs_2 + ... or lhs ~ rhs_1 + rhs_2 in case of identical LHS (see examples).

Details

Use "y ~ 0" to specify a stand alone LHS.

Note

This likely won't work for interaction terms (such as * or :).

Examples

# Combine everything (default)
combine_formulas(observed ~ rainfall + temp, observed ~ rainfall + forest.cover)
#> observed ~ rainfall + temp
#> <environment: 0x5654ac9c8308>
# Combine only LHS
combine_formulas(observed ~ rainfall + temp, observed ~ rainfall + forest.cover, combine = "lhs")
#> observed ~ rainfall + temp + rainfall + forest.cover
#> <environment: 0x5654ac9c8308>