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RItools (version 0.1-10)

plot.xbal: Plotting xBalance Objects

Description

A plot method for xBalance objects. WORK IN PROGRESS. PATCHES AND CODE SUGGESTIONS APPRECIATED.

We aim this plot to be a diagnostic tool rather than a publication quality presentation tool.

Usage

## S3 method for class 'xbal':
plot(x,adjustxaxis=.25,segments=TRUE,legend=TRUE,
                    mar=c(3,3,2,0)+0.1,mgp=c(1.5,.5,0),tck=-.01,
                    which.strata=dimnames(x$results)[["strata"]],thestratalabs=which.strata,
                    which.stats="std.diff", ##dimnames(x$results)[["stat"]],
                    which.vars=dimnames(x$results)[["vars"]],thevarlabs=which.vars,
                    thexlab="Standardized Differences",
                    thecols=rainbow(length(which.strata)),
                    thesymbols=c(19,22,23,24,25)[1:length(which.strata)],...)

Arguments

x
An object of class "xbal" --- the result of a call to xBalance()
adjustxaxis
amount by which the x-axis should be expanded.
segments
Should thin horizontal lines be plotted connecting the statistics for the different stratifications.
legend
Should a legend be plotted?
mar
Preliminary margin setting
mgp
Preliminary setting for axis labels
tck
Length of the tick marks
which.strata
The stratification candidates to include in the printout. Default is all.
thestratalabs
The text labels for the strata.
which.stats
a character vector of length 1. The test statistics to include. Default is the standardized difference.
which.vars
The variables for which test information should be displayed. Default is all.
thevarlabs
The text labels for the variables.
thexlab
The label for the x-axis (should tell viewers about the statistic chosen).
thecols
A vector of colors either (a) one per strata or (b) one for all strata.
thesymbols
A vector of plotting symbols either (a) one per strata or (b) one for all strata.
...
other arguments to the plot.default function setting up the plotting region.

Value

  • The plot allows a quick visual comparison of the effect of different stratification designs on the comparability of different variables. This is not a replacement for the omnibus statistical test reported as part of print.xbal. This plot does allow the analyst an easy way to identify variables that might be the primary culprits of overall imbalances and/or a way to assess whether certain important covariates might be imbalanced even if the omnibus test reports that the stratification overall produces balance.

References

xBalance

Examples

Run this code
data(nuclearplants)

xb0<-xBalance(pr~ date + t1 + t2 + cap + ne + ct + bw + cum.n,data=nuclearplants)

plot(xb0)

xb1<-xBalance(pr~ date + t1 + t2 + cap + ne + ct + bw + cum.n,
         strata=data.frame(unstrat=factor(character(32)),
           pt=factor(nuclearplants$pt)),
         data=nuclearplants,
         report=c("adj.means","adj.mean.diffs","std.diffs", "z.scores", "chisquare.test","p.values"))

plot(xb1)

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