extract_lhs: Extract the left hand side of a formula
Description
Extracts the left hand side from a formula object and returns it as
character string.
Relevant, for example, for survival formulas, where Surv(...) is a
call.
Usage
extract_lhs(formula)
Value
A character string.
Arguments
formula
a formula object (NOT a list of formulas)
Details
Internal; used in various help functions (2022-02-05)