R - display ≥ / more or equal on a forestplot - r

Question

I prepared the code for forestplot, however I have problem with exporting plot with "≥" / more or equal sign.
library(forestplot)
names6 <- c("Variable",
"A ≥ 4000***",
"B ≥ 50***",
"C**",
"D",
"E***",
"F",
"G*",
"H**",
"I*",
"J***")
coef6 <- c(0.42, 1.58, 1.35, 0.49,
0.46, 0.66, 0.62, 1.34, 0.52, 0.72)
low6 <- c(0.34, 1.29, 1.08, 0.21,
0.33, 0.44, 0.43, 1.08, 0.29, 0.61)
high6 <- c(0.51, 1.93, 1.69, 1.21,
0.64, 0.99, 0.91, 1.66, 0.92, 0.86)
boxsize6 <-c(0.2, 0.2, 0.2,0.2,
0.2,0.2, 0.2,0.2,
0.2, 0.2)
test_data <- data.frame(coef=coef6,
low=low6,
high=high6,
boxsize=boxsize6)
row_names <- cbind(names6,
c("OR",test_data$coef), c("CI-95%", test_data$low), c("CI+95%", test_data$high) )
test_data <- rbind(NA, test_data)
#####FIGURE
forestplot(labeltext = row_names,
mean = test_data$coef, upper = test_data$high,
lower = test_data$low,
is.summary=c(TRUE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE, FALSE),
boxsize = test_data$boxsize,
zero = 1,
xlog = FALSE,
xlab = "OR (95% CI)",
col = fpColors(lines="black", box="black"),
ci.vertices = TRUE,
xticks = c(0,0.5, 1, 1.5, 2.0),
colgap = unit(0.03,'npc'),
lineheight = unit(1.1,"cm"),
txt_gp=fpTxtGp(label = gpar(cex = 0.8),
title = gpar(cex = 1),
ticks = gpar(cex = 0.6),
xlab = gpar(cex = 0.7)))
However I cannot export plot as a .pdf file with present "≥" / more or equal.
Instead of this, I got sign "=" / equal.
What should I change to get this sign on plot?
Edit:
\u2265 do not work...

Answer 1

This solution might be system-specific. Here is something that works on windows:
library("forestplot")
library("withr")
names6 <- c("Variable",
"A \u2265 4000***",
"B \u2265 50***",
"C**",
"D",
"E***",
"F",
"G*",
"H**",
"I*",
"J***")
### Data & params code here....
with_cairo_pdf('forestplot.pdf',
### Forest plot code here....
forestplot(labeltext = row_names,
....)
)