%CEM Macro for SAS: Specifying variables for matching

Is it possible to specify a vector of variables to ignore during matching using the %CEM macro for SAS (available at: https://gking.harvard.edu/cem)?

As an example, consider a dataset called "Test" with the following variables:

Person_id: The ID primary key
Treatment: Treatment variable, equals 1 if an individual had treatment and 0 otherwise
X1: Binary auxiliary variable, e.g. gender
X2: Discrete auxiliary variable, e.g. age group
X3: Continuous auxiliary variable
Y: Outcome variable of interest.

The goal is to estimate the impact of "Treatment" on Y. First, we want to match treated observations with controls using only X1 and X2 during matching.

The cem {cem} command in R provides an option, "drop", which allows one to specify a vector of variables to ignore during matching:

cem(treatment="treatment", data=Test, drop=c("X3","Y"),k2k=FALSE)

Using cem in Stata, one can simply specify the variables to use in the matching procedure:

. cem X1 X2, tr(treatment)

Would it be possible to run the %CEM macro in SAS using only X1 and X2 for matching?

Solution

The latest version of %CEM allows one to specify a vector of variables to use in the matching process, i.e.:

%CEM (
      lib = work, 
      dataset = Test, 
      id = Person_id, 
      treat = Treatment, 
      keep = X1 X2,
      del_miss = 0,
      method = Sturges,
      path_graph = C:\path_graph,
      report = on
);