rggplot2labelsymbolssuperscript
how can I use math expressions in ggplot2 facet labels
In the following plot, I would like to replace "d" by delta, include a per mil symbol at the end, and use superscripts in: d13C, d15N and d34S.I got it when I use a biplot (e.g. plot + ylab(expression(paste(delta^{15}, "N (\u2030)")))). However, in the attached plot, I'm using facet_grid, which may change the way to get it. Here is the script used:
group.violin<-ggplot(group.data, aes(x=Culture2, group = Culture2, y=value)) +
stat_summary(aes(x = Culture2, y = value, color= Species, group = Species), fun = "mean",
geom = "line", lwd = 2, alpha = 0.5)+
stat_summary(geom="point")+
geom_violin(aes(x = Culture2, y = value, fill = Species), alpha = 0.4, color = NA)+
geom_point(aes(x = Culture2, y = value, fill = Species), size = 3, color = "black", pch = 21,
position = position_jitter(width = 0.05, seed = 12))+
facet_grid(variable ~ Species, scales = "free_y") +
xlab("")+
ylab("")+
theme_classic()+
theme(strip.background = element_rect(colour = "black", fill = "grey85", size = 0.1),
panel.border=element_rect(colour="black",size = 0.1, fill = NA),
panel.spacing = unit(0.3, "lines"),
axis.text.y = element_text(size = 12, colour = "black"),
axis.title.x = element_blank(),
axis.title.y = element_blank(),
legend.position = "bottom",
legend.text=element_text(size=12, face="italic"),
legend.title=element_text(size=12,face="bold"),
strip.text.x=element_text(size=12,face="bold.italic"),
strip.text.y=element_text(size=12,face="bold"))
Thank you
Solution
We can use sub to change your variable to be the labels you expect, then add labeller=label_parsed to the call to facet_grid.
Using my sample data (below), original plotting code:
group.data |>
transform(
variable2 = sub("d([0-9]+)(.*)", "delta^{\\1}*'\\2 (\u2030)'", variable)
) |>
ggplot(aes(x=Culture2, group = Culture2, y=value)) +
stat_summary(aes(x = Culture2, y = value, color= Species, group = Species), fun = "mean",
geom = "line", lwd = 2, alpha = 0.5)+
stat_summary(geom="point")+
geom_violin(aes(x = Culture2, y = value, fill = Species), alpha = 0.4, color = NA)+
geom_point(aes(x = Culture2, y = value, fill = Species), size = 3, color = "black", pch = 21,
position = position_jitter(width = 0.05, seed = 12))+
facet_grid(variable2 ~ Species, scales = "free_y", labeller = label_parsed) +
xlab("")+
ylab("")+
theme_classic()+
theme(strip.background = element_rect(colour = "black", fill = "grey85", size = 0.1),
panel.border=element_rect(colour="black",size = 0.1, fill = NA),
panel.spacing = unit(0.3, "lines"),
axis.text.y = element_text(size = 12, colour = "black"),
axis.title.x = element_blank(),
axis.title.y = element_blank(),
legend.position = "bottom",
legend.text=element_text(size=12, face="italic"),
legend.title=element_text(size=12,face="bold"),
strip.text.x=element_text(size=12,face="bold.italic"),
strip.text.y=element_text(size=12,face="bold"))
# No summary function supplied, defaulting to `mean_se()`
# No summary function supplied, defaulting to `mean_se()`
# No summary function supplied, defaulting to `mean_se()`
# No summary function supplied, defaulting to `mean_se()`
# No summary function supplied, defaulting to `mean_se()`
# No summary function supplied, defaulting to `mean_se()`
# No summary function supplied, defaulting to `mean_se()`
# No summary function supplied, defaulting to `mean_se()`
# No summary function supplied, defaulting to `mean_se()`
Unfortunately, this drops the bold/italic formatting you themed into the facet labels, so we need to be clearer on those. Further, having bold-italic in the facet strips and just italic in the other poses a small problem ... but I'll hack it into place by using plotmath-like "bolditalic(..)" expressions (strings) for everything, and then remove the bold portion of that string for just the legends.
For this step, we'll transform Species as well, then add scale_colour_discrete and _fill_ hacks using scales::label_parse for the labels= argument.
group.data |>
transform(
variable2 = sub("d([0-9]+)(.*)", "bold(delta^{\\1}*'\\2 (\u2030)')", variable),
Species = sprintf("bolditalic(%s)", Species)
) |>
ggplot(aes(x=Culture2, group = Culture2, y=value)) +
stat_summary(aes(x = Culture2, y = value, color= Species, group = Species), fun = "mean",
geom = "line", lwd = 2, alpha = 0.5)+
stat_summary(geom="point")+
geom_violin(aes(x = Culture2, y = value, fill = Species), alpha = 0.4, color = NA)+
geom_point(aes(x = Culture2, y = value, fill = Species), size = 3, color = "black", pch = 21,
position = position_jitter(width = 0.05, seed = 12))+
facet_grid(variable2 ~ Species, scales = "free_y", labeller = label_parsed) +
xlab("")+
ylab("")+
scale_colour_discrete(labels = function(z) scales::label_parse()(sub("bold","",z)))+
scale_fill_discrete(labels = function(z) scales::label_parse()(sub("bold","",z)))+
theme_classic()+
theme(strip.background = element_rect(colour = "black", fill = "grey85", size = 0.1),
panel.border=element_rect(colour="black",size = 0.1, fill = NA),
panel.spacing = unit(0.3, "lines"),
axis.text.y = element_text(size = 12, colour = "black"),
axis.title.x = element_blank(),
axis.title.y = element_blank(),
legend.position = "bottom",
legend.text=element_text(size=12),
legend.title=element_text(size=12,face="bold"),
strip.text.x=element_text(size=12),
strip.text.y=element_text(size=12))
Sample data:
set.seed(42)
n <- 420
group.data <- data.frame(Culture2 = sample(c("Auri", "Grav"), size=n, replace=TRUE), value=runif(n), Species=sample(c("Bos", "Cerv", "Equus"), size=n, replace=TRUE), variable=sample(c("d13C", "d15N", "d34S"), size=n, replace=TRUE))
head(group.data)
# Culture2 value Species variable
# 1 Auri 0.11483254 Equus d15N
# 2 Auri 0.48275690 Equus d13C
# 3 Auri 0.97917358 Equus d34S
# 4 Auri 0.81151679 Bos d13C
# 5 Grav 0.54291282 Equus d34S
# 6 Grav 0.07236709 Cerv d34S