matchdef {MatchIt} | R Documentation |
This is a sub-function of matchit
which performs the nearest neighbor
matching; matchdef
is called automatically by matchit
.
matchdef <- matchdef(formula, in.sample, pscore, covariates, nearest=TRUE, replace=FALSE, m.order=2, ratio=1, caliper=0, calclosest=FALSE, mahvars=NULL, exact=FALSE, data=NULL, 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. 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 |
Data frame containing the variables in formula . |
in.sample |
Vector of length n showing whether each unit was eligible for matching due to
common support restrictions with discard . Computed in distance . |
pscore |
Vector of propensity scores, calculated in distance . |
covariates |
Covariates from data frame used in matching process. Output from
distance . |
nearest |
Whether to perform nearest-neighbor matching (default=TRUE). |
replace |
Whether to match with replacement (default=FALSE). |
m.order |
Order in which to match treated units with control units. 2 (default)=from high to low, 3=from low to high, 4=random order. |
ratio |
The number of control units to be matched to each treated unit (default=1). |
caliper |
Standard deviations of the propensity score within which to draw control units (default=0). |
calclosest |
If caliper!=0 , whether to take the nearest available match if
no matches are available within caliper (default=FALSE). |
mahvars |
Variables on which to perform Mahalanobis matching within each caliper
(default=NULL). Should be entered as a vector of names of variables in data . |
exact |
"FALSE" (default)=no exact matching. "TRUE"=exact matching on all
variables in formula . A vector of variable names (that are in data ) to indicate
separate variables on which to exact match, in combination with matching on the propensity
score. |
counter |
Whether to display counter indicating the progress of the matching (default=TRUE). |
The matching is done using nearest neighbor matching on the propensity score, estimated
in the sub-function ref{distance}. 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.
match.matrix |
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. |
in.sample |
Vector of length n showing whether each unit was eligible for matching due to
common support restrictions with discard . |
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.