arm (version 1.15-1)

balance: Functions to compute the balance statistics

Description

This function computes the balance statistics before and after matching.

Usage

balance(rawdata, treat, matched, estimand="ATT")
# S3 method for balance
print(x, ..., combined = FALSE, digits = 2)
# S3 method for balance
plot(x, longcovnames=NULL, which.covs="mixed",
    v.axis=TRUE, cex.main=1, cex.vars=1, cex.pts=1,
    mar=c(4, 3, 5.1, 2), plot=TRUE, x.max = NULL, ...)

Details

This function plots the balance statistics before and after matching. The open circle dots represent the unmatched balance statistics. The solid dots represent the matched balance statistics. The closer the value of the estimates to the zero, the better the treated and control groups are balanced after matching.

References

Andrew Gelman and Jennifer Hill. (2006). Data Analysis Using Regression and Multilevel/Hierarchical Models. Cambridge University Press. (Chapter 10)

See Also

matching, par

Examples

# matching first
old.par <- par(no.readonly = TRUE)
data(lalonde)
attach(lalonde)
fit <- glm(treat ~ re74 + re75 + age + factor(educ) + 
            black + hisp + married + nodegr + u74 + u75, 
            family=binomial(link="logit"))
pscores <- predict(fit, type="link")
matches <- matching(z=lalonde$treat, score=pscores)
matched <- matches$cnts

# balance check
b.stats <- balance(lalonde, treat, matched, estimand = "ATT")
print(b.stats)
plot(b.stats)
par(old.par)