如何将标签添加到多个 ggplot 图（A、B、C）

Question

我正在尝试将标签 A、B 和 C 添加到每个图表的左上角。我试过cowplot::draw_plot_label()，但似乎没有任何效果。有人可以帮忙吗？

这些 A、B 和 C 标签并不是每个情节的主标题。

# Packages
library(ggplot2)
library(gridExtra)
library(cowplot)

# 1st plot
p1 <- ggplot(data = new_data %>% 
               filter(Species =="Sharksucker_Remora")) +
  scale_colour_manual(values=c(Sharksucker_Remora="black"), labels = c("Sharksucker Remora")) + 
  geom_line(mapping = aes(x = Date, y = Proportion, group = Species, colour = Species)) + 
  xlab("") + 
  ylab("Proportion") + 
  theme(legend.position="top") +
  theme(axis.text.x = element_text(angle = 90, vjust = 0.5, hjust = 1)) + labs(colour = ~italic(M.alfredi)~"Hitchhiker Species:") +
  theme(legend.key=element_blank())

# 2nd plot
p2 <- ggplot(data = new_data %>% 
               filter(Species !="Sharksucker_Remora")) +
  geom_line(mapping = aes(x = Date, y = Proportion, group = Species, colour = Species)) + 
  scale_colour_manual(values=c(Golden_Trevally="goldenrod2", Red_Snapper="firebrick2", Juvenile_Remora="darkolivegreen3"), labels = c("Juvenile Remora", "Golden Trevally", "Red Snapper")) + 
  xlab("") + ylab("Proportion") + labs(colour = "") + theme(legend.position="top") +  theme(legend.key=element_blank()) +
  theme(axis.text.x = element_text(angle = 90, vjust = 0.5, hjust = 1))

# 3rd plot
p3 <- ggplot(data = new_data_counts) +
  geom_bar(mapping = aes(x = Date, y = Count), stat =
             'identity') +
  xlab("Date (2015-2019)") +  ylab("Total"~italic
                                   (M.alfredi)~"Sightings") +
  draw_plot_label(label =c("C") + theme(axis.text.x =          
                                          element_text(angle = 90, vjust = 0.5, hjust   = 1))
                  
# The grid
grid.arrange(p1,p2,p3)

Answer 1

我建议你使用labs(..., tag = ...) 和theme(plot.tag = element_text())。 该代码显示了如何格式化主标题（此处以hjust = 0.5 为中心）和theme() 函数内的标签。请参阅下面的可重现示例：

# Packages
library(ggplot2)
library(gridExtra)
# library(cowplot) # not necessary here

# Plots
p1 <- ggplot() +
  labs(title = "plot 1", tag = "A") +
  theme(plot.title = element_text(hjust = 0.5),
        plot.tag = element_text())

p2 <- ggplot() +
  labs(title = "plot 2", tag = "B") +
  theme(plot.title = element_text(hjust = 0.5),
        plot.tag = element_text()) 

grid.arrange(p1, p2)

如果您希望标签（A、B、C）位于绘图区域内，this post 建议使用plot.tag.position = c(x, y)。例如：

p3 <- ggplot() +
  labs(title = "plot 3", tag = "C") +
  theme(plot.title = element_text(hjust = 0.5),
        plot.tag = element_text(),
        plot.tag.position = c(0.1, 0.8))
p3

Answer 2

你试过egg这个包吗？ https://cran.r-project.org/web/packages/egg/vignettes/Overview.html

library(tidyverse)
library(magrittr)
data <- list()
for(i in 1:6) data[[i]] <- rnorm(100,0,1)
data %<>% bind_cols() %>% setNames(paste0("var",1:6))
p1 <- ggplot(data,aes(x = var1, y = var2)) + geom_point()
p2 <- ggplot(data,aes(x = var3, y = var4)) + geom_point()
p3 <- ggplot(data,aes(x = var5, y = var6)) + geom_point()
egg::ggarrange(p1,p2,p3,ncol = 1,
               labels = c("A","B","C"))