The package has some functionality to modify the forestplot. Below is
the functions to edit various aspects of the plot:
Edit plot
Below is to make the total row text to bold and change the color of
the diamond shape. Then change the background color of the total row.
After that, align texts in the last six columns to the center.
# Change fontface
g <- edit_plot(p, row = 9,
gp = gpar(fontface = "bold"))
# Change color
g <- edit_plot(g, col = 8, row = 9, which = "ci",
gp = gpar(col = "blue", fill = "blue"))
# Change background of the total row
g <- edit_plot(g, col = 1:7,
row = 9,
which = "background",
gp = gpar(fill = "#f6eff7"))
# Align texts to center
g <- edit_plot(g, col = 9:14,
which = "text",
# gp = gpar(),
hjust = unit(0.5, "npc"),
x = unit(0.5, "npc"))
g
For the text align, hjust = unit(0, "npc") and
x = unit(0, "npc") to align left.
hjust = unit(0.5, "npc") and
x = unit(0.5, "npc") to align the text in the center.
hjust = unit(1, "npc") and
x = unit(0.9, "npc") to align right.
Add and insert text
In this step, we want to add some text to the header and total number
of events in the data.
# Add or insert some text to header on top of CI columns
g <- add_text(g, text = "IV, Random, 95% CI",
part = "header",
col = 7:8,
gp = gpar(fontface = "bold"))
g <- insert_text(g, text = "Odds ratio",
part = "header",
col = 7:8,
gp = gpar(fontface = "bold"))
# Group outcomes
g <- add_text(g, text = "Caffeine",
part = "header",
row = 1,
col = 2:3,
gp = gpar(fontface = "bold"))
g <- add_text(g, text = "Decaf",
part = "header",
row = 1,
col = 4:5,
gp = gpar(fontface = "bold"))
# Add text on the top of risk of bias data
g <- add_text(g, text = "Risk of Bias",
part = "header",
row = 1,
col = 9:14,
gp = gpar(fontface = "bold"))
# Insert event count
g <- insert_text(g,
text = c("Total events:"),
row = 9,
col = 1,
before = FALSE,
just = "left")
# Note: The row counts need to add one to account for
# `insert_text` in the previous step
g <- add_text(g, text = "58",
col = 2,
row = 10,
just = "left")
g <- add_text(g, text = "46",
col = 4,
row = 10,
just = "left")
g
Add borders
The next step we will add some borders at header. The default is to
add border at the bottom of the cell(s).
# Add or insert some text to header
g <- add_border(g,
part = "header",
row = 1,
col = 9:14,
gp = gpar(lwd = .5))
g <- add_border(g,
part = "header",
row = 2,
gp = gpar(lwd = 1))
g
Add grobs
In the next step, we will add a rounded rectangle border with dashed
line around the risk of bias data. Then draw circle grob with different
color at the bottom of the text.
g <- add_grob(g,
row = 1:c(nrow(dt_fig) - 1),
col = 9:14,
order = "backgroud",
gb_fn = roundrectGrob,
r = unit(0.05, "snpc"),
gp = gpar(lty = "dotted",
col = "#bdbdbd"))
# Draw circle grob, you can also draw a `pointsGrob`
cols <- c("#eeee00", "#00cc00", "#cc0000")
symb <- c("?", "+", "-")
for(i in seq_along(symb)){
pos <- which(dt_fig == symb[i], arr.ind=TRUE)
for(j in 1:nrow(pos)){
g <- add_grob(g,
row = pos[j,1],
col = pos[j,2],
order = "backgroud",
gb_fn = circleGrob,
r = 0.4,
gp = gpar(fill = cols[i]))
}
}
g
The text we are going to create involves with math expression and
multiple line. Any one of these can easily be done with
add_text and setting parse=TRUE. We can use
the code below to achieve what we want. The line break below is based on
the solution here
using the atop function. You can also use latex2exp
package for math expression.
txt <- bquote(atop(paste("Heterogeneity: ", tau^2, " = 0.22; ",
chi^2, " = 9.39, df = 6 (P = 0.15)",
I^2, " = 36%"),
"Total for overall effect: Z = 1.15(P=0.25)"))
add_text(g, text = txt,
col = 1:6,
row = 11,
just = "left",
parse = TRUE,
gp = gpar(fontsize = 8))
We can see that the second line is not left aligned, we can use
add_grob to take advantage of other packages that create
grobs object. Now we will use the gridtext package
to generate a complex text and add it to the plot with
add_grob. More details about the package can be found here. You can write
markdown or HTML text and render it to the plot. Currently is does not
support math equation. See other Unicode math symbols here
txt <- "Heterogeneity: τ<sup>2</sup> = 0.22; χ<sup>2</sup> = 9.39,
df=6 (P=0.15);I<sup>2</sup> = 36%<br><span style='color:blue'>**Total for overall effect:**</span> Z = 1.15(P=0.25)"
add_grob(g,
row = 11,
col = 1:6,
order = "backgroud",
gb_fn = gridtext::richtext_grob,
text = txt,
gp = gpar(fontsize = 8),
hjust = 0, vjust = 1, halign = 0, valign = 1,
x = unit(0, "npc"), y = unit(1, "npc"))
