如何在ggplot2的x轴上的每日数据之上添加月份？

Question

我有一个数据框，其中 Y 的降水量 (cm) 和 X 的天数。

> head(precip)
  Day     mean
1   1 1.784654
2   2 1.850796
3   3 1.850486
4   4 1.858424
5   5 1.884435
6   6 1.907781

直到 366 天（平均值包括闰年）。两列当前都是数字。这是我绘制它的代码：

precip_plots <- ggplot(data = precip, aes_string(x = "Day", y = "mean", group=1)) +
  geom_line(size = 1)+
  theme_bw()+
  labs(title = "Daily precipitation",
      x = "Day",
      y = "Precipitation (cm)")

看起来像

我希望日期在 X 轴上，但在下方（也在 X 轴上）我希望每个月的范围都有月份字母 (JFMAMJJASOND)，例如

我已尝试将此添加到 ggplot：

scale_x_discrete(limits = 1:366, labels=Day[1:31] = "J", Day[32:60] = "F", Day[61:91] = "M", 
                   Day[92:121] = "A", Day[122:152] = "M", Day[153:182] = "J", Day[183:213] = "J",
                   Day[214:244] = "A", Day[245:274] = "S", Day[275:305] = "O", Day[306:335] = "N", 
                   Day[336:366] = "D")

但它只是返回一堆“错误：意外'='”和“错误：意外'，'”。

我在网上和 SO 上到处找，似乎找不到任何有类似问题的人。

Answer 1

更新
这是在scale_x_continuous 中使用函数作为labels 参数的一种方法。仅当 breaks 包含所有天以及常规休息时间（100、200 等）时，此方法才有效。由于这会弄乱断线和轴刻度（它们不再对称），我用element_blank() 隐藏了它们，并用geom_vline 插入了自定义断线。

library(tidyverse)

# some toy data similar to the original data
dat <- tibble(Day = 1:366,
              mean = 2+rnorm(366))

# setup breaks
month <- c(31,60,91,121,152,182,213,244,274,305,335,365)
breaks <- seq(100,300,100)
mybreaks <- sort(c(month,breaks))

precip_plots <- ggplot(data = dat,
                       aes_string(x = "Day",
                                  y = "mean",
                                  group = 1)) +
  geom_line(size = 1) +
  scale_x_continuous(
    breaks = mybreaks,
    # custom function using `dplyr::case_when`
    labels = function(x) {
      
      case_when(
        x == 31  ~ "\nJ",
        x == 60  ~ "\nF",
        x == 91 ~ "\nM",
        x == 121 ~ "\nA",
        x == 152 ~ "\nM",
        x == 182 ~ "\nJ",
        x == 213 ~ "\nJ",
        x == 244 ~ "\nA",
        x == 274 ~ "\nS",
        x == 305 ~ "\nO",
        x == 335 ~ "\nN",
        x == 365 ~ "\nD",
        x %% 100 == 0 ~ as.character(x))
      
    }) +
  # creates fake break lines
  geom_vline(xintercept = breaks,
             color = "#d6d6d6",
             size = 0.5) + 
  theme_bw() +
  # hides original break lines and axis ticks
  theme(panel.grid.major.x = element_blank(),
        panel.grid.minor.x = element_blank(),
        axis.ticks.x = element_blank()
  ) +
  labs(title = "Daily precipitation",
       x     = "Day",
       y     = "Precipitation (cm)") 

precip_plots

^{由reprex package (v0.3.0) 于 2021-08-07 创建}