exactmatch {Matchit} | R Documentation |
exactmatch
is a sub-function of matchit
that does exact matching
on the set of covariates.
exactmatch <- exactmatch(formula, data, counter=TRUE)
formula |
(required). Takes the form of T ~ X1 + X2 , where T is a binary
treatment indicator and X1 and X2 are the pre-treatment covariates, and T ,
X1 , and X2 are contained in the same data frame. Exact matching is done on the
variables on the right-hand side of formula . |
data |
(required). Data frame containing the variables called in the formula .
The dataframe should not include variables with the names psclass , psweights , or
pscore , as these are expressly reserved in the output dataframe for MatchIt. |
counter |
Whether to display counter indicating the progress of the matching (default=TRUE). |
This sub-function is called automatically by the matchit
command when
exact=TRUE
is chosen, meaning exact matching on all covariates in the assignment model.
It creates subclasses defined by the values of the covariates, where each subclass must contain
some treated and some control units. Units with no exact matches in the other treatment group
are discarded. This function is called directly by matchit
and does not generally need
to be called directly by users; these details are included for advanced users.
psclass |
Subclass index in an ordinal scale from 1 to the number of subclasses.
Unmatched units have subclass=0. With exact matching, these subclasses are defined by the
categories of the variables in formula . |
Daniel Ho <deho@fas.harvard.edu>; Kosuke Imai <kimai@princeton.edu>; Gary King <king@harvard.edu>; Elizabeth Stuart<stuart@stat.harvard.edu>
Please use help.matchit
to access the matchit reference
manual. The complete document is available online at
http://gking.harvard.edu/matchit.