Convert a Matching Result to a matchit Object

Constructs a matchit-class S3 object from a couplr result, enabling use with any function that accepts MatchIt objects (e.g., cobalt, marginaleffects).

Usage

as_matchit(
  result,
  left,
  right,
  formula = NULL,
  left_id = "id",
  right_id = "id",
  estimand = NULL,
  ...
)

Arguments

result: A couplr result object (matching_result, full_matching_result, cem_result, or subclass_result)
left: Data frame of left (treated) units
right: Data frame of right (control) units
formula: Optional formula used for matching. If not provided, a default formula is constructed from result$info$vars.
left_id: Name of ID column in left (default: "id")
right_id: Name of ID column in right (default: "id")
estimand: Target estimand stamped on the matchit object: one of "ATT", "ATC" or "ATE". NULL (default) reads it from the design, which every couplr front door records as info$estimand. MatchIt and marginaleffects read this field to pick the target population and the weighting of the effect estimate, so give it explicitly whenever the design does not determine it – in particular when left holds the controls, which makes the design's left-focal weighting an ATC.
...: Additional arguments (ignored)

Value

An S3 object of class "matchit" with fields:

match.matrix: Match matrix (treated x controls)
treat: Named treatment vector (1/0)
weights: Matching weights
X: Covariate matrix
call: Original call
info: Metadata from couplr

Examples

if (requireNamespace("MatchIt", quietly = TRUE)) {
  set.seed(1)
  left <- data.frame(id = 1:5, age = c(25, 35, 45, 55, 65))
  right <- data.frame(id = 6:15, age = runif(10, 20, 70))
  result <- match_couples(left, right, vars = "age")
  mi <- as_matchit(result, left, right)
  mi
  if (requireNamespace("cobalt", quietly = TRUE)) cobalt::bal.tab(mi)
}