如何将x轴从数字更改为自定义ggplot？

Question

我的数据看起来像：

require(ggplot2); require(lubridate); require(data.table); require(dplyr)

Date  <- rep(seq.Date(as.Date("2014-01-01"), as.Date("2016-12-31"), by = "days"), 3)
Index <- rep(c(rep(1:365, times = 2), 1:366), 3)
Counts<- sample(1:25, size = length(Index), replace = TRUE)
City  <- rep(c("Dallas", "San Antonio", "Houston"), each = length(Index)/3)

df    <- data.frame(Date = Date, Index = Index, Counts = Counts, City = City)

df    <- df %>% mutate(Year = year(as.Date(Date)))

我使用以下代码绘制数据：

ggplot(df, aes(x = Index, y = Counts, colour = City)) +
  geom_line(aes(group = City))+
  geom_vline(xintercept = c(31, 59.5, 90, 120, 151, 181, 212, 243, 273, 304, 334))+
  facet_grid(Year~.) +
  theme(legend.position = "bottom")

我的目标是将x轴标记为 Jan Feb ... Dec 。我试过scale_x_continuous和scale_x_discrete但没有用。有什么建议吗？

提前致谢

Answer 1

如果您使用Date作为x变量并使用scale_x_date，我认为这更容易实现：

df <- df %>% mutate(Year = year(as.Date(Date)),
                    MonthStart = round_date(Date, unit = "month"))

mid_months <- seq.Date(as.Date("2014-01-15"), as.Date("2016-12-15"), by = "months")

ggplot(df, aes(x = Date, y = Counts, colour = City)) +
    geom_line(aes(group = City))+
    facet_wrap(~ Year, ncol = 1, scales = "free") +
    geom_vline(aes(xintercept = MonthStart), colour = 'black') +
    # expand = c(0,0) to ensure scale doesn't extend to additional
    #   months
    scale_x_date(breaks = mid_months, date_labels = "%b", expand = c(0, 0)) +
    theme(legend.position = "bottom")

编辑：已更新以添加月中标签

Answer 2

利用您已经获得的内容的快速选项是将x截取的向量作为中断传递给scale_x_continuous，并使用month.abb命名它们：

library(tidyverse)

df <- data_frame(
    Date = rep(seq.Date(as.Date("2014-01-01"), as.Date("2016-12-31"), by = "days"), 3),
    Index = rep(c(rep(1:365, times = 2), 1:366), 3),
    Counts = sample(1:25, size = length(Index), replace = TRUE),
    City = rep(c("Dallas", "San Antonio", "Houston"), each = length(Index) / 3),
    Year = lubridate::year(Date)
)

month_breaks <- c(31, 59.5, 90, 120, 151, 181, 212, 243, 273, 304, 334)

ggplot(df, aes(x = Index, y = Counts, colour = City)) +
    geom_line() +
    geom_vline(xintercept = month_breaks) +
    scale_x_continuous(breaks = month_breaks, labels = month.abb[-1]) +
    facet_grid(Year ~ .) +
    theme(legend.position = "bottom")