The metafor Package

A caterpillar plot is in essence nothing different than what is often called a forest plot in the meta-analytic literature, except that the estimates are ordered by their magnitude. Also, the term tends to be used under circumstances where the number of estimates is rather large, so focus is on showing the general pattern of the results and not making individual estimates fully discernible. The code below shows how such a plot can be created with the forest() function. In case this is needed, one can also add a summary polygon to the bottom of the plot.

library(metafor)
 
### simulate some data
set.seed(5132)
k <- 250
vi <- rchisq(k, df=1) * .03
yi <- rnorm(k, rnorm(k, 0.5, 0.4), sqrt(vi))
 
### fit RE model
res <- rma(yi, vi)
 
### create plot
forest(yi, vi,
       header=FALSE,            # suppress the header
       xlim=c(-2.5,3.5),        # adjust the horizontal plot limits
       ylim=c(-8,254),          # adjust the vertical plot limits
       order="est",             # order the studies by the estimates
       slab=NA, annotate=FALSE, # remove the study labels and annotations
       efac=c(0,1),             # remove the vertical bars at end of the CIs
       pch=19,                  # change the point symbol to a filled circle
       colci="gray40",          # change the color of the CIs
       psize=2.5,               # use a constant point size of 2.5
       cex.lab=1, cex.axis=1,   # set the size of x-axis title/labels
       lty=c("solid","blank"))  # remove the horizontal line at top of the plot
 
### add summary polygon at bottom and text
addpoly(res, mlab="", cex=1)
text(-2, -2, "RE Model", pos=4, offset=0, cex=1)