Change font in metafor R

Question

I have copied this code I have found on the metafor page - package for R. However, when I run it, I get the forest plot but with the classic Arial font in my plot instead of the font that is displayed in the preview figure on the website. How can I solve this? It doesn't strictly need to be the same font on the website, but I would like to understand why the font is not the same and also how to change the font.

Thank you!

### create the dataset (from Goldenberg et al., 2021; http://dx.doi.org/10.1136/bmj.m4743)
dat <- data.frame(author = c("Dyson", "Jönsson", "Morris", "Saslow", "Saslow", "Sato", "Tay", "Yamada"),
                  year   = c(2010, 2009, 2019, 2014, 2017, 2017, 2014, 2014),
                  ai     = c(3, 6, 11, 8, 6, 4, 36, 2),
                  n1i    = c(6, 6, 21, 9, 11, 22, 46, 12),
                  ci     = c(1, 3, 0, 5, 0, 0, 30, 2),
                  n2i    = c(6, 6, 12, 13, 8, 27, 47, 12))
 
### calculate risk differences and corresponding sampling variances (and use
### the 'slab' argument to store study labels as part of the data frame)
dat <- escalc(measure="RD", ai=ai, n1i=n1i, ci=ci, n2i=n2i, data=dat,
              slab=paste(" ", author, year), addyi=FALSE)
dat
 
### fit random-effects model (using the DL estimator)
res <- rma(yi, vi, data=dat, method="DL")
res
 
############################################################################
 
### colors to be used in the plot
colp <- "#6b58a6"
coll <- "#a7a9ac"
 
### total number of studies
k <- nrow(dat)
 
### generate point sizes
psize <- weights(res)
psize <- 1.2 + (psize - min(psize)) / (max(psize) - min(psize))
 
### get the weights and format them as will be used in the forest plot
weights <- fmtx(weights(res), digits=1)
 
### adjust the margins
par(mar=c(2.7,3.2,2.3,1.3), mgp=c(3,0,0), tcl=0.15)
 
### forest plot with extra annotations
sav <- forest(dat$yi, dat$vi, xlim=c(-3.4,2.1), ylim=c(-0.5,k+3), alim=c(-1,1), cex=0.88,
              pch=18, psize=psize, efac=0, refline=NA, lty=c(1,0), xlab="",
              ilab=cbind(paste(dat$ai, "/", dat$n1i), paste(dat$ci, "/", dat$n2i), weights),
              ilab.xpos=c(-1.9,-1.3,1.2), annosym=c(" (", " to ", ")"),
              rowadj=-.07)
 
### add the vertical reference line at 0
segments(0, -1, 0, k+1.6, col=coll)
 
### add the vertical reference line at the pooled estimate
segments(coef(res), 0, coef(res), k, col=colp, lty="33", lwd=0.8)
 
### redraw the CI lines and points in the chosen color
segments(summary(dat)$ci.lb, k:1, summary(dat)$ci.ub, k:1, col=colp, lwd=1.5)
points(dat$yi, k:1, pch=18, cex=psize*1.15, col="white")
points(dat$yi, k:1, pch=18, cex=psize, col=colp)
 
### add the summary polygon
addpoly(res, row=0, mlab="Total (95% CI)", efac=2, col=colp, border=colp)
 
### add the horizontal line at the top
abline(h=k+1.6, col=coll)
 
### redraw the x-axis in the chosen color
axis(side=1, at=seq(-1,1,by=0.5), col=coll, labels=FALSE)
 
### now we add a bunch of text; since some of the text falls outside of the
### plot region, we set xpd=NA so nothing gets clipped
par(xpd=NA)
 
### adjust cex as used in the forest plot and use a bold font
par(cex=sav$cex, font=2)
 
### add headings
text(sav$xlim[1], k+2.5, pos=4, "Study or\nsubgroup")
text(sav$ilab.xpos[1:2], k+2.3, c("Experimental","Control"))
text(mean(sav$ilab.xpos[1:2]), k+3.4, "No of events / total")
text(0, k+2.7, "Risk difference, IV,\nrandom (95% CI)")
segments(sav$ilab.xpos[1]-0.22, k+2.8, sav$ilab.xpos[2]+0.13, k+2.8)
text(c(sav$ilab.xpos[3],sav$xlim[2]-0.35), k+2.7, c("Weight\n(%)","Risk difference, IV,\nrandom (95% CI)"))
 
### add 'Favours control'/'Favours experimental' text below the x-axis
text(c(-1,1), -2.5, c("Favors control","Favors experimental"), pos=c(4,2), offset=-0.3)
 
### use a non-bold font for the rest of the text
par(cex=sav$cex, font=1)
 
### add the 100.0 for the sum of the weights
text(sav$ilab.xpos[3], 0, "100.0")
 
### add the column totals for the counts and sample sizes
text(sav$ilab.xpos[1:2], 0, c(paste(sum(dat$ai), "/", sum(dat$n1i)), paste(sum(dat$ci), "/", sum(dat$n2i))))
 
### add text with heterogeneity statistics
text(sav$xlim[1], -1, pos=4, bquote(paste("Test for heterogeneity: ",
   tau^2, "=", .(fmtx(res$tau2, digits=2)), "; ",
   chi^2, "=", .(fmtx(res$QE, digits=2)),
   ", df=", .(res$k - res$p), ", ",
   .(fmtp(res$QEp, digits=2, pname="P", add0=TRUE, equal=TRUE)), "; ",
   I^2, "=", .(round(res$I2)), "%")))
 
### add text for test of overall effect
text(sav$xlim[1], -2, pos=4, bquote(paste("Test for overall effect: ",
   "Z=", .(fmtx(res$zval, digits=2)), ", ",
   .(fmtp(res$pval, digits=3, pname="P", add0=TRUE, equal=TRUE)))))

Answer 1

Assuming you want to save the plot as a png file (as was done in the example), you just need to use the family argument of png() to adjust the font. For example, assuming you have the InterFace font installed, then png(filename="forest_plot_bmj.png", res=350, width=3312, height=1228, family="InterFace") should work (don't forget the dev.off() at the end and check what the font is actually called on your system).