findexact {bigmatch}

Build an exact match variable given a matrix of covariates ordered by the user according to their importance.

Description

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.

Usage

findexact(z, E, ncontrol=1)

Arguments

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.

Value

miss

The covariates that cannot be exactly matched.

variables

The covariates that can be exactly matched.

NewExact

The constructed exact match variable.

Examples

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)