R ggplot使用facet_wrap时如何给指定分面修改背景色实现高亮

实现方法 #

theme()为全局样式控制函数，无法直接映射分面变量值单独修改指定分面样式，可通过新增背景图层的方式实现需求，无需额外安装扩展包，具体操作如下：

1. 构造高亮分面的数据集，仅需指定需要高亮的topicr取值：

highlight_bg <- data.frame(
  topicr = c(37, 42)
)

2. 将背景图层放在所有绘图图层的最前端，保证后续的线、点等元素显示在背景上方，修改后的完整代码如下：

library(ggplot2)
library(scales)

axr_treat_ctrl %>%  
  ggplot(aes(x= year, y= mtopic,colour= Type,group=Type))+
  # 新增高亮背景层，inherit.aes=FALSE避免继承全局映射参数
  geom_rect(data = highlight_bg, 
            aes(xmin = -Inf, xmax = Inf, ymin = -Inf, ymax = Inf),
            fill = "lightblue", alpha = 0.3,
            inherit.aes = FALSE)+
  geom_line( )+
  geom_point(size = 1) +
  scale_y_continuous(breaks = extended_breaks(n = 5))+
  scale_x_continuous(breaks = extended_breaks(n = 10))+
  geom_vline(xintercept = 2005, linetype=2, color= "brown")+  
  geom_vline(xintercept = c(2010,2011,2017), linetype=3, color= "blue")+  
  labs(x = "x-axis",
       y = "y-axis")+
  facet_wrap(~topicr)+
  guides(x = guide_axis(angle = 90))+
  theme(legend.position = "bottom")

如果需要更精细的面板样式控制，也可以使用ggh4x扩展包的facet_wrap2()函数，直接按分面指定面板背景：

library(ggplot2)
library(scales)
library(ggh4x)

axr_treat_ctrl %>%  
  ggplot(aes(x= year, y= mtopic,colour= Type,group=Type))+
  geom_line( )+
  geom_point(size = 1) +
  scale_y_continuous(breaks = extended_breaks(n = 5))+
  scale_x_continuous(breaks = extended_breaks(n = 10))+
  geom_vline(xintercept = 2005, linetype=2, color= "brown")+  
  geom_vline(xintercept = c(2010,2011,2017), linetype=3, color= "blue")+  
  labs(x = "x-axis",
       y = "y-axis")+
  facet_wrap2(~topicr,
              theme = theme(
                panel.background = element_rect(fill = ifelse(
                  as.numeric(levels(factor(topicr)))[.x] %in% c(37,42),
                  "lightblue", "white"
                ))
              ))+
  guides(x = guide_axis(angle = 90))+
  theme(legend.position = "bottom")

内容的提问来源于stack exchange，提问作者Jian Zhang