plots:forest_plot_with_multiple_cis

The question has come up how one can draw a forest plot where multiple confidence intervals with different confidence levels are shown for the same set of studies. To accomplish this, we can use a trick where we draw the same forest plot twice on top of each other (using `par(new=TRUE)`

) and then adjust the line width (using `lwd`

) so that the wider confidence intervals are drawn using a thicker line. The second time the plot is drawn, we suppress several elements (i.e., the points, annotations, the vertical reference line, the study labels, the x-axis and its label, and the horizontal line) so that these elements are not drawn twice.

A related question asked about the possibility to draw the confidence interval of the pooled estimate (from a random-effects model) using a different level than the one that is used for the studies. This can be accomplished by adding the pooled estimate to the plot using `addpoly()`

and changing the `level`

.

The example below illustrates both of these possibilities.

library(metafor) ### copy BCG vaccine meta-analysis data into 'dat' dat <- dat.bcg ### calculate log risk ratios and corresponding sampling variances dat <- escalc(measure="RR", ai=tpos, bi=tneg, ci=cpos, di=cneg, data=dat, slab=paste(author, year, sep=", ")) ### draw forest plot with 95% CIs for the studies with(dat, forest(yi, vi, xlim=c(-8,6), ylim=c(-1.5,nrow(dat)+3), psize=1, efac=0, header=TRUE)) ### superimpose forest plot with 80% CIs for the studies par(new=TRUE) with(dat, forest(yi, vi, xlim=c(-8,6), ylim=c(-1.5,nrow(dat)+3), level=80, lwd=3, psize=NA, efac=NA, annotate=FALSE, refline=NA, slab=NA, xaxt="n", xlab="", lty=c("solid","blank"))) ### fit random-effects model res <- rma(yi, vi, data=dat) ### add pooled estimate to the forest plot with a 99% CI addpoly(res, row=-1, level=99, mlab="RE Model (with 99% CI)", annotate=TRUE) ### add a horizontal line between the studies and the pooled estimate abline(h=0)

plots/forest_plot_with_multiple_cis.txt ยท Last modified: 2021/12/20 15:41 by Wolfgang Viechtbauer

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