parse_formula: Parse model formula.
In GegznaV/BioStat: Routines for Basic (Bio)Statistics

Parse model formula, create new variables by evaluating expressions and return parsed names and new data frame. These elements are ment to be used by other functions.

1	parse_formula(formula, data = NULL, keep_all_vars = FALSE)

formula

A stats::formula() of form:

~ y;
~ y1 + y2;
y ~ x;
y1 + y2 ~ x1 + x2;
~ y|condition;
y ~ x|condition;
y1 + y2 ~ x1 + x2|cond1 + cond2;
or similar.

Variables can be expressed as function, e.g., log(x), as.factor(x), which will be evaluated. Dot (.) is not accepted.

data

A data frame.

keep_all_vars

(logical) Flag indicating if all variables (even those not in formula) should be included in the output data. Expression keep_all_vars = TRUE has effect only if data is a data frame (and not NULL or an environment).

A list with fields:

formula - the formula used;
names - alist of character vectors with names in formula arranged in certain way (see below);
data - a data frame with variables and evaluated expressions in the formula and, optionally, with the remaining variables from the original data frame.

Contents of the field names:

all_names - all names (and expressions) in the formula;
y, x - names for "x" and "y" variables (except condition variables);
lhs, rhs - names in left-hand and right-hand side of formula (except condition variables);
condition - names of condition variables and expressions;
gr - if condition exists, gr is the same as condition, otherwise it is the same as x.