#===========================================================
#code for Chapter 5 "Propensity Score Matching" of book:
#Leite, W. L. (2017). Practical propensity score methods using R. 
#Thousand Oaks, CA: Sage. 

#PART 6 - OPTIMAL ONE TO ONE MATCHING WITHOUT REPLACEMENT
# 
#this is the code that was used to generate the example results in the book
#As the R software and the R packages used in this example are updated frequently
#some incompatibilities between the current code and new R versions or package versions
#may appear
#Any updates to the code will be posted at:
# http://www.practicalpropensityscore.com


#This example estimates the effect of mothers having a job 
#that provides or subsidizes child care 
#on the length that they breastfeed their children 
#National Longitudinal Survey of Youth 1979 (NLSY79) 
#and the NLSY79 Children and Youth

#Perform optimal one-to-one matching  without replacement

library(MatchIt) #library for propensity score matching
library(optmatch)

#load data
load(file="Chapter5_data_with_propensity_scores_and_formula.rData")

#run the matching altorighm
optimalMatching <- matchit(psFormula,distance=data$logitPScores, 
                        data = data, method = "optimal", ratio=1)


#diagnose covariate balance
(balance.optimalMatching <- summary(optimalMatching, standardize=T))
#obtain the summary of balance after matching 
summary(abs(balance.optimalMatching$sum.matched$"Std. Mean Diff."))
table(abs(balance.optimalMatching$sum.matched$"Std. Mean Diff.") > 0.1)



#------------------------------------------
#estimate ATT with one-to-one optimal matched data
#using regression

#obtain matched data
data.optimalMatching <- match.data(optimalMatching)

library(survey)
design.optimalMatching <- svydesign(ids=~subclass, weights=~weights,
                                    data=data.optimalMatching)
#fit regression model
model.optimalMatching <- svyglm(C0338600~childCare, design.optimalMatching, family=gaussian())
summary(model.optimalMatching)