View source: R/add_s.weights.R
add_s.weights  R Documentation 
matchit
objectAdds sampling weights to a matchit
object so that they are
incorporated into balance assessment and creation of the weights. This would
typically only be used when an argument to s.weights
was not supplied
to matchit()
(i.e., because they were not to be included in the estimation
of the propensity score) but sampling weights are required for generalizing
an effect to the correct population. Without adding sampling weights to the
matchit
object, balance assessment tools (i.e., summary.matchit()
and plot.matchit()
) will not calculate balance statistics correctly, and
the weights produced by match.data()
and get_matches()
will not
incorporate the sampling weights.
add_s.weights(m, s.weights = NULL, data = NULL)
m 
a 
s.weights 
an numeric vector of sampling weights to be added to the

data 
a data frame containing the sampling weights if given as a
string or formula. If unspecified, 
a matchit
object with an s.weights
component
containing the supplied sampling weights. If s.weights = NULL
, the original
matchit
object is returned.
Noah Greifer
matchit()
; match.data()
data("lalonde")
# Generate random sampling weights, just
# for this example
sw < rchisq(nrow(lalonde), 2)
# NN PS match using logistic regression PS that doesn't
# include sampling weights
m.out < matchit(treat ~ age + educ + race + nodegree +
married + re74 + re75, data = lalonde)
m.out
# Add s.weights to the matchit object
m.out < add_s.weights(m.out, sw)
m.out #note additional output
# Check balance; note that sample sizes incorporate
# s.weights
summary(m.out, improvement = FALSE)
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