ggplot2: how to extend y-axis labels across stacked figures - r

Question

I have a dataframe of daily mean temperature observations for a year from two locations (i.e., Site 1 & Site 2). The three temperature variables are:
Air temperature
Water temperature
Difference = Air - Water
I would like to produce a four-panel figure where the top and bottom rows are Site 1 and Site 2 respectively, the left column displays Air and Water and the right column shows Difference. I am specifically not using facet_wrap() or facet_grid() because the y-axes are two different variables (i.e., temperature and temperature difference), and the legends are custom.
I can create the four-panel figure however, I would like the y-axis title for each column not to be repeated. Is there a way to extend each y-axis title across the stacked plots for each column?
Here is the output from the figure code below
The ideal figure would look something more like this
Example Data
library(data.table)
library(dplyr)
library(ggplot2)
library(patchwork)
set.seed(321)
# Create the example air and water temperature time series
df1 <- data.frame(matrix(ncol = 4, nrow = 365*4))
colnames(df1)[1:4] <- c("Location","Variable", "Date", "Temperature")
df1[1:730,1] <- "Site 1"
df1[731:NROW(df1),1] <- "Site 2"
df1[c(1:365,731:1095),2] <- "Air"
df1[c(366:730,1096:NROW(df1)),2] <- "Water"
df1$Date <- rep(seq.Date(as.Date("2021-01-01"),as.Date("2021-12-31"),"1 day"),4)
df1$noise <- rep(runif(365),4)
df1$t <- rep(seq(0,1*pi,,365),4)
for (i in 1:NROW(df1)) {
df1$Temperature[1:365] <- 20*sin(df1$t)+df1$noise*8
df1$Temperature[365:730] <- 17*sin(df1$t)+df1$noise*2
df1$Temperature[731:1095] <- 25*sin(df1$t)+df1$noise*6
df1$Temperature[1096:NROW(df1)] <- 18*sin(df1$t)+df1$noise*1.5
}
# Take the difference between air and water temperature
df1 <- df1[,1:4]
site1 <- df1[df1$Location == 'Site 1',]
site1 <- site1 %>%
tidyr::pivot_wider(names_from = Variable, values_from = Temperature) %>%
mutate(Difference = Air - Water)
site2 <- df1[df1$Location == 'Site 2',]
site2 <- site2 %>%
tidyr::pivot_wider(names_from = Variable, values_from = Temperature) %>%
mutate(Difference = Air - Water)
Code for figure
fig1a <- site1 %>%
ggplot() +
geom_line(aes(x = Date, y = Air), color = "red", size = 1) +
geom_line(aes(x = Date, y = Water), size = 1, alpha = 0.7) +
scale_x_date(date_breaks = "2 month",
date_labels = "%b",
expand = c(0, 0)) +
labs(x = NULL,
y = expression(paste("Temperature ( ", degree, "C)"))) +
annotate("rect", fill = "white", color = "black",
xmin = as.Date("2021-01-15", "%Y-%m-%d"),
xmax = as.Date("2021-03-15", "%Y-%m-%d"),
ymin = 26, ymax = 30) +
annotate("segment", color = "red", size = 1,
x = as.Date("2021-01-20", "%Y-%m-%d"),
xend = as.Date("2021-01-30", "%Y-%m-%d"),
y = 29, yend = 29) +
annotate("segment", color = "black", size = 1,
x = as.Date("2021-01-20", "%Y-%m-%d"),
xend = as.Date("2021-01-30", "%Y-%m-%d"),
y = 27, yend = 27) +
annotate("text", x = as.Date("2021-02-01", "%Y-%m-%d"), y = 29,
label = 'Air',
size = 5, fontface = 1, hjust = 0) +
annotate("text", x = as.Date("2021-02-01", "%Y-%m-%d"), y = 27,
label = "Water",
size = 5, fontface = 1, hjust = 0) +
annotate("text", x = as.Date("2021-11-30", "%Y-%m-%d"), y = 30,
label = "(a",
size = 6, fontface = 1, hjust = 0) +
theme_bw() +
theme(plot.margin = unit(c(0, 1, 0, 1), "lines"),
panel.grid = element_blank(),
text = element_text(size = 16),
axis.text.x = element_text(size = 14, color = "white"),
axis.text.y = element_text(size = 14, color = "black"),
panel.border = element_blank()) +
guides(fill = guide_legend(nrow = 2)) +
coord_cartesian(clip = 'off', ylim = c(0, 32)) +
annotation_custom(grid::rectGrob(gp = grid::gpar(fill = NA)))
fig1b <- site2 %>%
ggplot() +
geom_line(aes(x = Date, y = Air), color = "red", size = 1) +
geom_line(aes(x = Date, y = Water), size = 1, alpha = 0.7) +
scale_x_date(date_breaks = "2 month",
date_labels = "%b",
expand = c(0, 0)) +
labs(x = NULL,
y = expression(paste("Temperature ( ", degree, "C)"))) +
annotate("text", x = as.Date("2021-11-30", "%Y-%m-%d"), y = 30,
label = "(b",
size = 6, fontface = 1, hjust = 0) +
theme_bw() +
theme(plot.margin = unit(c(0, 1, 2, 0), "lines"),
panel.grid = element_blank(),
text = element_text(size = 16),
axis.text.x = element_text(size = 16, color = "black", angle = 90, vjust = 0.5, hjust = 1),
axis.text.y = element_text(size = 16, color = "black"),
panel.border = element_blank()) +
guides(fill = guide_legend(nrow = 2)) +
coord_cartesian(clip = 'off', ylim = c(0,32)) +
annotation_custom(grid::rectGrob(gp = grid::gpar(fill = NA))) +
annotate(geom = "text", x = as.Date("2021-06-15", "%Y-%m-%d"), y = -7, label = 2021, size = 6)
fig1c <- site1 %>%
ggplot() +
geom_line(aes(x = Date, y = Difference), size = 1) +
scale_x_date(date_breaks = "2 month",
date_labels = "%b",
expand = c(0, 0)) +
labs(x = NULL,
y = expression(paste(Delta~" Temperature ( ", degree, "C)"))) +
annotate("rect", fill = "white", color = "black",
xmin = as.Date("2021-01-15", "%Y-%m-%d"),
xmax = as.Date("2021-06-01", "%Y-%m-%d"),
ymin = 10.25, ymax = 12.5) +
annotate("text", x = as.Date("2021-01-20", "%Y-%m-%d"), y = 12,
label = 'Pos. = Air > Water',
size = 5, fontface = 1, hjust = 0) +
annotate("text", x = as.Date("2021-01-20", "%Y-%m-%d"), y = 11,
label = "Neg. = Water > Air",
size = 5, fontface = 1, hjust = 0) +
annotate("text", x = as.Date("2021-11-30", "%Y-%m-%d"), y = 12,
label = "(c",
size = 6, fontface = 1, hjust = 0) +
theme_bw() +
theme(plot.margin = unit(c(0, 1, 0, 0), "lines"),
panel.grid = element_blank(),
text = element_text(size = 16),
axis.text.x = element_text(size = 14, color = "white"),
axis.text.y = element_text(size = 14, color = "black"),
panel.border = element_blank()) +
guides(fill = guide_legend(nrow = 2)) +
coord_cartesian(clip = 'off', ylim = c(-2, 12)) +
annotation_custom(grid::rectGrob(gp = grid::gpar(fill = NA)))
fig1d <- site2 %>%
ggplot() +
geom_line(aes(x = Date, y = Difference), size = 1) +
scale_x_date(date_breaks = "2 month",
date_labels = "%b",
expand = c(0, 0)) +
labs(x = NULL,
y = expression(paste(Delta~" Temperature ( ", degree, "C)"))) +
annotate("text", x = as.Date("2021-11-30", "%Y-%m-%d"), y = 12,
label = "(d",
size = 6, fontface = 1, hjust = 0) +
theme_bw() +
theme(plot.margin = unit(c(1, 1, 2, 0), "lines"),
panel.grid = element_blank(),
text = element_text(size = 16),
axis.text.x = element_text(size = 16, color = "black", angle = 90, vjust = 0.5, hjust = 1),
axis.text.y = element_text(size = 16, color = "black"),
panel.border = element_blank()) +
guides(fill = guide_legend(nrow = 2)) +
coord_cartesian(clip = 'off', ylim = c(-2,12)) +
annotation_custom(grid::rectGrob(gp = grid::gpar(fill = NA))) +
annotate(geom = "text", x = as.Date("2021-06-15", "%Y-%m-%d"), y = -5, label = 2021, size = 6)
# width = 1200 height = 900
fig1a + fig1c + fig1b + fig1d + plot_layout(ncol = 2)

Answer 1

I figured out how to do it, which required using facet_grid. I ended up needing to create two facets that I then stitched together, see below.
# Take the difference between air and water temperature
df1 <- df1[,1:4]
site1 <- df1[df1$Location == 'Site 1',]
site1 <- site1 %>%
tidyr::pivot_wider(names_from = Variable, values_from = Temperature) %>%
mutate(Difference = Air - Water) %>%
tidyr::pivot_longer(cols = c('Water','Air','Difference'),
names_to = 'Variable',
values_to = 'Temperature')
site2 <- df1[df1$Location == 'Site 2',]
site2 <- site2 %>%
tidyr::pivot_wider(names_from = Variable, values_from = Temperature) %>%
mutate(Difference = Air - Water) %>%
tidyr::pivot_longer(cols = c('Water','Air','Difference'),
names_to = 'Variable',
values_to = 'Temperature')
df1 <- rbind(site1,site2)
# This creates the first column of figures
p1 <- df1 %>%
subset(!df1$Variable == 'Difference',) %>%
mutate(var_air_water = ## Here is the new variable
if_else(Variable %in% c("Air", "Water"),
true = "Air & Water",
false = Variable)) %>%
ggplot() +
geom_line(aes(x = Date, y = Temperature, group = Variable, color = Variable)) +
scale_color_manual(values = c("black", "red")) +
scale_x_date(date_breaks = "2 month",
date_labels = "%b",
expand = c(0, 0)) +
scale_y_continuous(breaks = seq(0,30,5)) +
labs(x = NULL,
y = expression(paste("Temperature ( ", degree, "C)"))) +
theme_bw() +
theme(plot.margin = unit(c(0, 1, 2, 0), "lines"),
panel.grid = element_blank(),
text = element_text(size = 16),
axis.text.x = element_text(size = 16, color = "black", angle = 90, vjust = 0.5, hjust = 1),
axis.text.y = element_text(size = 16, color = "black"),
legend.title = element_blank(),
legend.text = element_text(size = 16),
legend.position = c(0.15,0.95),
legend.background = element_blank(),
strip.text = element_blank(),
strip.background = element_blank(),
panel.border = element_blank()) +
guides(fill = guide_legend(nrow = 2)) +
coord_cartesian(clip = 'off', ylim = c(0,33)) +
annotation_custom(grid::rectGrob(gp = grid::gpar(fill = NA))) +
annotate(geom = "text", x = as.Date("2021-06-15", "%Y-%m-%d"), y = -8, label = 2021, size = 6) +
facet_grid(Location~var_air_water)
# This adds the text to the corresponding figures
dat_text1 <- data.frame(
label = c("(a","(b"),
Location = c('Site 1','Site 2'),
x = c(as.Date("2021-12-01", "%Y-%m-%d"),
as.Date("2021-12-01", "%Y-%m-%d")),
y = c(32,32))
p1 <- p1 + geom_text(
data = dat_text1,
mapping = aes(x = x, y = y, label = label,
hjust = 0,
vjust = 1),
size = 5)
# This creates the second column of figures
p2 <- df1 %>%
mutate(var_air_water = ## Here is the new variable
if_else(Variable %in% c("Air", "Water"),
true = "Air & Water",
false = Variable)) %>%
subset(!var_air_water == c('Air & Water'),) %>%
ggplot() +
geom_line(aes(x = Date, y = Temperature, group = Variable, color = Variable)) +
scale_color_manual(values = "black") +
scale_x_date(date_breaks = "2 month",
date_labels = "%b",
expand = c(0, 0)) +
scale_y_continuous(breaks = seq(0,12,2)) +
labs(x = NULL,
y = expression(paste(Delta~" Temperature ( ", degree, "C)"))) +
theme_bw() +
theme(plot.margin = unit(c(0, 1, 2, 0), "lines"),
panel.grid = element_blank(),
text = element_text(size = 16),
axis.text.x = element_text(size = 16, color = "black", angle = 90, vjust = 0.5, hjust = 1),
axis.text.y = element_text(size = 16, color = "black"),
legend.position = 'none',
strip.background = element_rect(fill = "gray80"),
strip.background.x = element_blank(),
strip.text.x = element_blank(),
strip.text.y = element_text(size = 16)) +
guides(fill = guide_legend(nrow = 2)) +
coord_cartesian(clip = 'off', ylim = c(0,12)) +
annotation_custom(grid::rectGrob(gp = grid::gpar(fill = NA))) +
annotate(geom = "text", x = as.Date("2021-06-15", "%Y-%m-%d"), y = -3, label = 2021, size = 6) +
facet_grid(Location~var_air_water)
# Like above, this adds the text to the corresponding figures
dat_text2 <- data.frame(
label = c("Pos. = Air > Water", "Neg. = Water > Air", "(c","(d"),
Location = c('Site 1','Site 1','Site 1','Site 2'),
x = c(as.Date("2021-01-15", "%Y-%m-%d"),
as.Date("2021-01-15", "%Y-%m-%d"),
as.Date("2021-12-01", "%Y-%m-%d"),
as.Date("2021-12-01", "%Y-%m-%d")),
y = c(12,11,12,12))
p2 <- p2 + geom_text(
data = dat_text2,
mapping = aes(x = x, y = y, label = label,
hjust = 0,
vjust = 1,
size = 10),
size = 5)
# width = 1200 height = 900
p1 + p2 + plot_layout(ncol = 2)