subclassify {MatchIt}R Documentation

Subclassify units

Description

This is a sub-function of matchit which generates subclasses of units given a propensity score.

Usage

subclassify <- subclassify(formula, data, in.sample, pscore, nearest=TRUE, match.matrix, 
                subclass=0, sub.by="treat", counter=TRUE)

Arguments

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. The + symbol means "inclusion" not "addition." You may also include interaction terms in the form if I(X1*X2) or squared terms in the form of I(X1^2).
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.
in.sample (required). Vector of length n showing whether each unit was eligible for matching due to common support restrictions with discard. Generally created by distance.
pscore (required). Vector of estimated propensity scores. Generally created by distance.
nearest Whether to perform nearest-neighbor matching (default=TRUE).
match.matrix (required) n1 by ratio data frame where the rows correspond to treated units and the columns store the names of the control units matched to each treated unit. NA indicates that treated unit was not matched. Generally created by matchdef.
subclass Either a scaler specifying the number of subclasses (default=0) or a vector of probabilities to create quantiles based on sub.by.
sub.by If subclass!=0, by what criteria to subclassify. "treat" (default) =by the number of treated units, "control"=by the number of control units, "all"=by the total number of units.
counter Whether to display counter indicating the progress of the matching (default=TRUE).

Details

This function creates subclasses of units based on their covariate values, usually defined by the propensity score. 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.

Value

psclass Subclass index in an ordinal scale from 1 to the number of subclasses. Unmatched units have subclass=0.
q.cut Subclass cut points.

Author(s)

Daniel Ho <deho@fas.harvard.edu>; Kosuke Imai <kimai@princeton.edu>; Gary King <king@harvard.edu>; Elizabeth Stuart<stuart@stat.harvard.edu>

See Also

Please use help.matchit to access the matchit reference manual. The complete document is available online at http://gking.harvard.edu/matchit.


[Package MatchIt version 0.1-8 Index]