formula: formula used to calculate the distance measure
for matching (e.g., the propensity score model). It takes the usual syntax of R formulas, treat
~ x1 + x2, where treat is a binary treatment indicator,
and x1 and x2 are the pre-treatment covariates. Both the
treatment indicator and pre-treatment covariates must be contained
in the same data frame, which is specified as data (see
below). All of the usual R syntax for formulas work here. For
example, x1:x2 represents the first order interaction term
between x1 and x2, and I(x1 ^ 2) represents the
square term of x1. See help(formula) for details.
data: the data frame containing the variables called in
formula.
method: the matching method (default =
"nearest", nearest neighbor matching). Currently,
"exact" (exact matching), "full" (full matching),
"nearest" (nearest neighbor matching), "optimal"
(optimal matching), "subclass" (subclassification),
"genetic" (genetic matching), and "cem" (coarsened
exact matching) are available. Note that within each of these
matching methods, MATCHIT offers a variety of options. See below
for more details.
verbose: a logical value indicating whether to print
the status of the matching algorithm (default = FALSE).
