metafor (version 0.5-0)

addpoly.default: Add Polygons to Forest Plot

Description

Function to add one or more polygons to a forest plot.

Usage

## S3 method for class 'default':
addpoly(x, vi, sei, row=-1, level=95, digits=2, annotate=TRUE, 
        mlab=NULL, transf=FALSE, atransf=FALSE, targs=NULL, 
        col="black", efac=1, cex=NULL, ...)

Arguments

x

a vector with the values at which the polygons should be drawn.

vi

a vector with the corresponding variances.

sei

a vector with the corresponding standard errors. (note: only one of the two, vi or sei, needs to be specified)

row

integer specifying the (starting) row of where the polygon(s) should be placed (default is -1).

level

a numerical value between 0 and 100 specifying the confidence interval level (default is 95).

digits

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

annotate

logical specifying whether annotations should be added to the plot for the polygons that are drawn (default is TRUE).

mlab

optional character vector with the same length as x giving labels for the polygons that are drawn. Defaults to NULL, which suppresses labels.

transf

an optional argument specifying the name of a function that should be used to transform the x values and confidence interval bounds. 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 polygons that are drawn (default is "black").

efac

vertical expansion factor for the polygons. 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 one or more polygons to an existing forest plot created with the forest function. For example, summary estimates based on a subgrouping of the studies or from models involving moderators can be added to the plot this way. See examples below. The arguments transf, atransf, efac, and cex should always be set equal to the same values used to create the forest plot.

See Also

forest.rma, forest.default

Examples

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

### meta-analysis of the log risk rates using a mixed-
### effects model with absolute latitude as moderator
res <- rma(ai=tpos, bi=tneg, ci=cpos, di=cneg, mods=cbind(ablat),
           slab=paste(author, year), data=dat.bcg, measure="RR", method="REML")

### forest plot of the observed risk rates
forest(res, addfit=FALSE, atransf=exp, addrows=3, xlab="Relative Risk (log scale)")

### predicted log average risk rates for 10, 30, and 50 degrees absolute latitude
x <- predict(res, newmods=c(10, 30, 50))

### add predicted average risk rates to forest plot
addpoly(x$pred, sei=x$se, atransf=exp, 
        mlab=c("10 Degrees", "30 Degrees", "50 Degrees"))