shift.cem: Diagnostic tool for CEM

In cem: Coarsened Exact Matching

Diagnostic tool for CEM

Description

Diagnostic tools for CEM. Applies leftward and rightward shifts of the cutpoints.

Usage

shift.cem(obj, data, shifts=NULL, verbose=1, plot=TRUE)

Arguments

obj	and object of class cem
data	the original data
shifts	a vector of proportions of shifts
verbose	controls the level of verbosity
plot	whether to plot a graphic representation of the search

Details

For each variable, shift all the cutpoints left and right by shifts times the smallest epsilon of the coarsening. Shifting to the right produces a new cell on the left; shift to the left, adds a new cell to the coarsening on the right. Only positive proportions should be used; the algorithm will produce shifting on the left or on the right. The best shifting of the original cem match is produced as output, where best is defined in terms of the maximal total number of matched units mT+mC (see below).

By default, the function returns minimal information about the execution of the algorithm. By setting a value greater than 0 in option verbose more feedback on the process is returned.

Option plot = TRUE plots the number of treated units matched mT, the number of control units matched mC, and the sum mT+mC, as a function of the shifts.

Value

tab	an invisible object containing a new cem object

Author(s)

Stefano Iacus, Gary King, and Giuseppe Porro

References

Iacus, King, Porro (2011) doi: 10.1198/jasa.2011.tm09599

Iacus, King, Porro (2012) doi: 10.1093/pan/mpr013

Iacus, King, Porro (2019) doi: 10.1017/pan.2018.29

See Also

cem

Examples

data(LL)
set.seed(123)
m74 <- max(LL$re74, na.rm=TRUE)
s74 <- seq(0,m74,by=sd(LL$re74))
l74 <- length(s74)
if(max(s74) < m74) s74 <- c(s74, m74)

m75 <- max(LL$re75, na.rm=TRUE)
s75 <- seq(0,m75,by=sd(LL$re75))
l75 <- length(s75)
if(max(s75) < m75) s75 <- c(s75, m75)

mybr = list(re74=s74, 
 re75 = s75,
 age = hist(LL$age,plot=FALSE)$breaks,
 education = hist(LL$education,plot=FALSE)$breaks)

mat <- cem(treatment="treated",data=LL, drop="re78",cut=mybr)
mat

shift.cem(mat, data=LL, shifts=seq(0.01, 0.5, length=10), verb=1)

cem documentation built on Sept. 8, 2022, 5:09 p.m.