addpoly.rma: Add Summary Estimate Polygon to Forest Plot

Description

Function to add a polygon to a forest plot showing the summary estimate with correspondong confidence interval based on an object of class "rma".

Usage

## S3 method for class 'rma':
addpoly(x, row=-2, level=x$level, digits=2, annotate=TRUE, 
        mlab=NULL, transf=FALSE, atransf=FALSE, targs=NULL, 
        col="black", efac=1, cex=NULL, \dots)

Arguments

an object of class "rma".

row

value specifying the row (or more generally, the horizontal position) for plotting the polygon (default is -2).

level

a numerical value between 0 and 100 specifying the confidence interval level (the default is to take the value from the object).

digits

integer value specifying the number of decimal places to which the annotations should be rounded (default is 2).

annotate

logical specifying whether annotations for the summary estimate should be added to the plot (default is TRUE).

mlab

optional character string giving a label for the summary estimate polygon. Defaults to NULL, which means that the label is created within the function.

transf

an optional argument specifying the name of a function that should be used to transform the summary estimate and confidence interval bound. Defaults to FALSE, which means that no transformation is used.

atransf

an optional argument specifying the name of a function that should be used to transform the annotations. Defaults to FALSE, which means that no transformation is used.

targs

optional arguments needed by the function specified via transf or atransf.

col

color of the polygon that is drawn (default is "black").

efac

vertical expansion factor for the polygon. The default value of 1 should usually work okay.

cex

an optional symbol expansion factor. If NULL (default), the function tries to set this to a sensible value.

...

other arguments.

Details

The function can be used to add a polygon to an existing forest plot created with the forest function. The polygon shows the summary estimate based on a fixed- or random-effects model. The arguments transf, atransf, efac, and cex should always be set equal to the same values used to create the forest plot.

References

Viechtbauer, W. (2010). Conducting meta-analyses in R with the metafor package. Journal of Statistical Software, 36(3), 1--48. http://www.jstatsoft.org/v36/i03/.

Examples

Run this code

### load BCG vaccine data
data(dat.bcg)

### meta-analysis of the log relative risks using the Mantel-Haenszel method
res <- rma.mh(ai=tpos, bi=tneg, ci=cpos, di=cneg, data=dat.bcg, 
              slab=paste(author, year, sep=", "), measure="RR")

### forest plot of the observed relative risks with summary estimate
forest(res, atransf=exp, ylim=c(-2.5,16))

### meta-analysis of the log relative risks using a random-effects model
res <- rma(ai=tpos, bi=tneg, ci=cpos, di=cneg, 
           data=dat.bcg, measure="RR", method="REML")

### add summary estimate from the random-effects model to forest plot
addpoly(res, atransf=exp)