I have 50 control subjects and I would like to get 150 treatment subjects (i.e., a 1:3 ratio between the control and treatment groups) using propensity score matching and a few covariates. After performing the matching I would like to get indices of matched subjects (i.e., indices for both control and treatment groups) – this is my main goal.
I would like to do this in R. I see that R has the Matchit and Matching packages. However, I am not sure what the difference is between the two and which one is more appropriate for my purpose.
I am also not sure about the code and what output I need to be looking at to get indices of the matched control and treatment subjects.
Also, could I use the match() command without the outcome (i.e., Y) variable? The experiment is not yet complete and thus I do not have the outcome variable. Would it be appropriate to use match(Y=NULL, Tr=.....)?
Best Answer
Have a look at an overview here: http://www.biostat.jhsph.edu/~estuart/propensityscoresoftware.html
Match package does, as Charlie mentioned, let you exclude the outcome variable and will provide you with matching only then.