parse_formula: Parse formula for brokenstick model
Description
A bare bones formula parser to extract variables names from
formulas of y ~ x | g. It return the name of
the first variable mentioned in each formula component.
Usage
parse_formula(f)
Arguments
f
formula object
Value
A list with elements x, y and g.
Each element has length 1.
# NOT RUN {# examples that yield identical resultparse_formula(y ~ x | z)
parse_formula(y + a ~ x + x1 | z + b)
parse_formula(y + a + log(b) ~ x + x1 * c | z + d)
# }