如何修改R语言ggplot2中facet_wrap分面堆叠条形图的x轴刻度

解决方案 #

你可以按以下步骤修改代码实现需求：

1. 首先设置facet_wrap的scales = "free_x"参数，允许每个分面独立设置x轴刻度标签
2. 提前提取所有周数+年份组合对应的唯一日期，自定义scale_x_discrete的标签生成逻辑，自动匹配每个分面对应的日期

修改后的完整可运行代码如下：

library(ggplot2)
library(dplyr)

dat <- data.frame(date = as.Date(c("2021-01-03", "2020-01-05", "2021-01-03", "2020-01-05", "2021-01-03", "2021-01-03", "2021-01-10","2020-01-12", "2021-01-10", "2020-01-12", "2021-01-10", "2021-01-10", "2021-01-17", "2020-01-19", "2021-01-17", "2020-01-19", "2021-01-17", "2021-01-17")),
                 total = c(109334, 150052, 36546, 51476, 2961, 19988, 106719, 126748, 31893, 
                           29576, 5401, 19336, 91021, 108892, 23030, 26115, 3861, 15663),
                 product = c("A", "A","B", "B", "C", "D", "A", "A", "B", "B", "C", "D", "A", 
                              "A","B", "B", "C", "D"),
                 week = c(1,1,1,1,1,1,2,2,2,2,2,2,3,3,3,3,3,3),
                 year = c(2021,2020,2021,2020,2021,2021,2021,2020,2021,2020,2021,2021,2021,2020,2021,2020,2021,2021))  

# 提前生成每个周和年份对应的唯一日期标签
date_labels <- dat %>% 
  distinct(week, year, date) %>% 
  # 可自行调整日期显示格式，这里示例为月/日/年
  mutate(date_str = format(date, "%m/%d/%y"))

dat %>% 
  # x轴转因子保证2020在前、2021在后的固定顺序
  ggplot(aes(factor(year), total, color = year == 2021, fill = product)) +
  geom_bar(position = "stack", stat = "identity", size =0.6)+
  scale_y_continuous(expand = c(0,0), breaks = seq(0, 350000, by = 50000), limits=c(0, 350000))+
  # 自定义x轴标签，匹配当前分面的周数对应的日期
  scale_x_discrete(
    labels = function(x) {
      cur_week <- ggplot2::cur_data()$week[1]
      date_labels$date_str[date_labels$week == cur_week & date_labels$year == as.integer(x)]
    }
  ) +
  scale_color_manual(values = c(NA, 'red'), guide=F)+
  # 允许分面使用独立x轴刻度
  facet_wrap(~week, nrow = 1, scales = "free_x")+
  theme(axis.text.x=element_text(angle = 90, vjust =0, hjust =0),
        axis.title.x = element_blank(),
        axis.title.y = element_blank(),
        panel.background = element_blank(),
        panel.grid.major = element_blank(), 
        panel.grid.minor = element_blank(),
        panel.spacing.x = unit(0.1, "lines"))

运行上述代码即可实现每个分面x轴显示对应周的两个年份的周日日期的效果。

内容的提问来源于stack exchange，提问作者Jota3go