findexact | R Documentation |
The function is used to build an exact match variable given a matrix of covariates ordered by the user according to their importance. It will select as many important covariates as possible.
findexact(z, E, ncontrol=1)
z |
A vector whose ith coordinate is 1 for a treated unit and is 0 for a control. |
E |
A matrix or a vector with length(z) rows giving the covariates that need to be exactly matched. |
ncontrol |
The number of controls to be matched to each treated individual. |
miss |
The covariates that cannot be exactly matched. |
variables |
The covariates that can be exactly matched. |
NewExact |
The constructed exact match variable. |
data(nh0506) attach(nh0506) # The following example uses all of the variables in the propensity score,propens ex<-findexact(z,cbind(female,age,education,black,hispanic,povertyr)) head(ex$miss) head(ex$variables) table(z,ex$NewExact) # In order to exact match on age as well # one option is to divide age into several levels age_quantile<-as.integer(cut(age,quantile(age,c(0,0.25,0.5,0.75,1)))) ex2<-findexact(z,cbind(female,age_quantile,education,black,hispanic,povertyr,bmi)) head(ex2$miss) head(ex2$variables) table(z,ex2$NewExact) detach(nh0506)
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