两行带有嵌套 x 变量的轴标签(年份低于月份) [英] Axis labels on two lines with nested x variables (year below months)

问题描述

我想沿水平轴显示月份(以缩写形式)，并打印一次相应的年份.我知道如何显示月-年:

一年中不必要的重复使标签变得混乱.相反，我想要这样的东西:

除了年份将打印在月份下方.

我在轴标签上方打印了年份，因为这是我能做的最好的事情.这遵循 annotate() 函数的限制，如果它位于绘图区域之外，则会被剪裁.我知道基于 annotate_custom() 的可能解决方法，但我无法让它们与日期对象一起使用(我没有尝试将日期转换为数字并再次转换回日期，看起来比希望需要的更复杂)

我想知道是否可以为此目的劫持新的 dup_axis().如果不是将复制的轴发送到面板的另一侧，而是将其发送到复制轴下方几行，那么也许只需使用 panel.grid.major<设置一个轴即可/code> 空白且标签设置为 %b，而另一个轴将 panel.grid.minor 空白且标签设置为 %Y.(一个额外的挑战是年份标签将改为 10 月而不是 1 月)

这些问题是相关的.但是，据我所知，annotate_custom() 函数和 textGrob() 函数不能很好地处理日期.

请注意，使用这种方法，如果在一年的开始或结束时缺少日期(通过缺少"，我的意思是这些日期的行甚至不存在于数据中)，那么 x 轴将开始/结束于该年数据的第一个/最后一个日期，而不是从 1 月 1 日到 12 月 31 日.在这种情况下，您需要为缺少的日期添加行，并为 value 添加 NA 或插入 value.此外，这种方法在一年的 12 月 31 日和次年的 1 月 1 日之间没有空格或线，因此每年都有不连续性.

选项 1b:分面 + 居中的月份标签

解决@AF7 的评论.您可以通过在每个标签前添加一些空格来使月份标签居中.但是您必须手动选择空格数，具体取决于打印到设备时绘图的物理大小.(可能有一种方法可以根据内部 grob 测量以编程方式使标签居中，但我不知道该怎么做.)我还删除了较小的垂直网格线并减轻了年份之间的界限.

ggplot(df, aes(Date, value)) +geom_line() +scale_x_date(date_labels=paste(c(rep(" ",11), "%b"), collapse=""),date_breaks="月", expand=c(0,0)) +facet_grid(~ year(Date), space="free_x", scales="free_x", switch="x") +主题_bw() +主题(strip.placement =外部"，strip.background = element_blank(),panel.grid.minor.x = element_blank(),panel.border = element_rect(color="grey70"),panel.spacing=unit(0,"cm"))

选项 2a:编辑 x 轴标签 grob

这是一种更复杂和挑剔的方法(尽管它可能会由比我更了解网格图形的结构和单位间距的人自动化)，它避免了上述分面方法的缺陷:

库(网格)# 为说明添加了额外年份的假数据set.seed(2)df = data.frame(Date=seq(as.Date("1718-03-01"),as.Date("1721-09-20"), by="1 day"))df$value = cumsum(rnorm(nrow(df)))# 我们要开始的情节p = ggplot(df, aes(日期, 值)) +geom_vline(xintercept=as.numeric(df$Date[yday(df$Date)==1]), colour="grey60") +geom_line() +scale_x_date(date_labels="%b", date_breaks="month", expand=c(0,0)) +主题_bw() +主题(panel.grid.minor.x = element_blank()) +实验室(x="")

现在我们要在下面和每年的 6 月和 7 月之间添加年份值.下面的代码通过修改 x 轴标签 grob 来实现这一点，并改编自 @SandyMuspratt 的 this SO answer.

# 获取 grobg <- ggplotGrob(p)# 获取y轴index <- which(g$layout$name == "axis-b") # 哪个 grobxaxis <- g$grobs[[索引]]# 获取刻度(标签和标记)滴答声 <- xaxis$children[[2]]# 获取标签滴答声B <-滴答声$grobs[[2]]# 编辑 x 轴标签 grob# 在 x 轴标签中查找 Jun 的每个索引并添加换行符和# 然后是年份标签六月 = which(ticksB$children[[1]]$label == "Jun")ticksB$children[[1]]$label[junes] = paste0(ticksB$children[[1]]$label[junes],"
 ", 唯一的(年(df$Date)))# 将编辑后的标签放回图中滴答声$grobs[[2]] <- 滴答声Bxaxis$children[[2]] <- 刻度g$grobs[[index]] <- xaxis# 绘制情节grid.newpage()网格绘制(g)

选项 2b:编辑 x 轴标签 grob 并将月份标签居中

下面是唯一需要对选项 2a 进行更改以使月份标签居中的更改，但需要再次手动调整空格数.

# 进行编辑# 在刻度之间居中月份标签ticksB$children[[1]]$label = paste0(paste(rep(" ",7),collapse=""), ticksB$children[[1]]$label)# 在x轴标签和年份标签中查找Jun的每个索引junes = grep("Jun", ticksB$children[[1]]$label)ticksB$children[[1]]$label[junes] = paste0(ticksB$children[[1]]$label[junes], "
", unique(year(df$Date)))

I would like to display months (in abbreviated form) along the horizontal axis, with the corresponding year printed once. I know how to display month-year:

The un-needed repetition of the year clutters the labels. Instead I would like something like this:

except that the year would be printed below the months.

I printed the year above the axis labels, because that's the best I could do. This follows a limitation of the annotate() function, which gets clipped if it lies outside of the plot area. I am aware of possible workarounds based on annotate_custom(), but I couldn't make them to work with date objects (I did not try to convert dates to numbers and back to dates again, as it seemed more complicated than hopefully necessary)

I'm wondering if the new dup_axis() could be hijacked for this purpose. If instead of sending the duplicated axis to the opposite side of the panel, it could send it a few lines below the duplicated axis, then perhaps it would just be a matter of setting up one axis with panel.grid.major blanked out and the labels set to %b, while the other axis would have panel.grid.minor blanked out and the labels set to %Y. (an added challenge is that the year labels would be shifted to October instead of January)

These questions are related. However, the annotate_custom() function and textGrob() functions do not play well with dates, as far as I can tell.

how-can-i-add-annotations-below-the-x-axis-in-ggplot2

displaying-text-below-the-plot-generated-by-ggplot2

Data and basic code below:

    library("ggplot2")
    library("scales")
    ggplot(data = df, aes(x = Date, y = value)) + geom_line() +
        scale_x_date(date_breaks = "2 month", date_minor_breaks = "1 month", labels = date_format("%b %Y")) +
        xlab(NULL)

    ggplot(data = df, aes(x = Date, y = value)) + geom_line() +
        scale_x_date(date_minor_breaks = "2 month", labels = date_format("%b")) +   
        annotate(geom = "text", x = as.Date("1719-10-01"), y = 0, label = "1719") +
        annotate(geom = "text", x = as.Date("1720-10-01"), y = 0, label = "1720") +
        xlab(NULL)


    # data
    df <- structure(list(Date = structure(c(-91455, -91454, -91453, -91452, 
    -91451, -91450, -91448, -91447, -91446, -91445, -91444, -91443, 
    -91441, -91440, -91439, -91438, -91437, -91436, -91434, -91433, 
    -91431, -91430, -91429, -91427, -91426, -91425, -91424, -91423, 
    -91422, -91420, -91419, -91418, -91417, -91416, -91415, -91413, 
    -91412, -91411, -91410, -91409, -91408, -91406, -91405, -91404, 
    -91403, -91402, -91401, -91399, -91398, -91397, -91396, -91395, 
    -91394, -91392, -91391, -91390, -91389, -91388, -91387, -91385, 
    -91384, -91382, -91381, -91380, -91379, -91377, -91376, -91375, 
    -91374, -91373, -91372, -91371, -91370, -91369, -91368, -91367, 
    -91366, -91364, -91363, -91362, -91361, -91360, -91359, -91357, 
    -91356, -91355, -91354, -91353, -91352, -91350, -91349, -91348, 
    -91347, -91346, -91345, -91343, -91342, -91341, -91340, -91339, 
    -91338, -91336, -91335, -91334, -91333, -91332, -91331, -91329, 
    -91328, -91327, -91326, -91325, -91324, -91322, -91321, -91320, 
    -91319, -91315, -91314, -91313, -91312, -91311, -91310, -91308, 
    -91307, -91306, -91305, -91304, -91303, -91301, -91300, -91299, 
    -91298, -91297, -91296, -91294, -91293, -91292, -91291, -91290, 
    -91289, -91287, -91286, -91285, -91284, -91283, -91282, -91280, 
    -91279, -91278, -91277, -91276, -91275, -91273, -91272, -91271, 
    -91270, -91269, -91268, -91266, -91265, -91264, -91263, -91262, 
    -91261, -91259, -91258, -91257, -91256, -91255, -91254, -91252, 
    -91251, -91250, -91249, -91248, -91247, -91245, -91244, -91243, 
    -91242, -91241, -91240, -91238, -91237, -91236, -91235, -91234, 
    -91233, -91231, -91230, -91229, -91228, -91227, -91226, -91224, 
    -91223, -91222, -91221, -91220, -91219, -91217, -91216, -91215, 
    -91214, -91213, -91212, -91210, -91209, -91208, -91207, -91205, 
    -91201, -91200, -91199, -91198, -91196, -91195, -91194, -91193, 
    -91192, -91191, -91189, -91188, -91187, -91186, -91185, -91184, 
    -91182, -91181, -91180, -91179, -91178, -91177, -91175, -91174, 
    -91173, -91172, -91171, -91170, -91168, -91167, -91166, -91165, 
    -91164, -91163, -91161, -91160, -91159, -91158, -91157, -91156, 
    -91154, -91153, -91152, -91151, -91150, -91149, -91147, -91146, 
    -91145, -91144, -91143, -91142, -91140, -91139, -91138, -91131, 
    -91130, -91129, -91128, -91126, -91125, -91124, -91123, -91122, 
    -91121, -91119, -91118, -91117, -91116, -91115, -91114, -91112, 
    -91111, -91110, -91109, -91108, -91107, -91104, -91103, -91102, 
    -91101, -91100, -91099, -91097, -91096, -91095, -91094, -91093, 
    -91091, -91090, -91089, -91088, -91087, -91086, -91084, -91083, 
    -91082, -91081, -91080, -91079, -91077, -91076, -91075, -91074, 
    -91073, -91072, -91070, -91069, -91068, -91065, -91063, -91062, 
    -91061, -91060, -91059, -91058, -91056, -91055, -91054, -91053, 
    -91052, -91051, -91049, -91048, -91047, -91046, -91045, -91044, 
    -91042, -91041, -91040, -91039, -91038, -91037, -91035, -91034, 
    -91033, -91032, -91031, -91030, -91028, -91027, -91026, -91025, 
    -91024, -91023, -91021, -91020, -91019, -91018, -91017, -91016, 
    -91014, -91013, -91012, -91011, -91010, -91009, -91007, -91006, 
    -91005, -91004, -91003, -91002, -91000, -90999, -90998, -90997, 
    -90996, -90995, -90993, -90992, -90991, -90990, -90989, -90988, 
    -90986, -90985, -90984, -90983, -90982), class = "Date"), value = c(113, 
    113, 113, 113, 114, 114, 114, 115, 115, 115, 116, 116, 116, 116, 
    117, 117, 117, 117, 116, 117, 116, 116, 116, 117, 117, 117, 117, 
    117, 117, 117, 116, 117, 116, 116, 116, 117, 117, 117, 117, 117, 
    117, 117, 116, 116, 117, 117, 117, 117, 117, 117, 117, 117, 117, 
    117, 117, 118, 118, 118, 118, 117, 118, 117, 117, 117, 117, 117, 
    117, 118, 116, 116, 116, 116, 116, 116, 116, 117, 117, 118, 118, 
    118, 118, 118, 119, 120, 120, 119, 119, 120, 120, 121, 121, 122, 
    124, 124, 122, 123, 124, 123, 123, 123, 123, 123, 124, 124, 126, 
    126, 126, 126, 126, 125, 125, 126, 127, 126, 126, 125, 126, 126, 
    126, 128, 128, 128, 130, 133, 131, 133, 134, 134, 134, 136, 136, 
    136, 135, 135, 135, 136, 136, 136, 136, 135, 135, 135, 135, 130, 
    129, 129, 130, 131, 136, 138, 155, 157, 161, 170, 174, 168, 165, 
    169, 171, 181, 184, 182, 179, 181, 179, 175, 177, 177, 174, 170, 
    174, 173, 178, 173, 178, 179, 182, 184, 184, 180, 181, 182, 182, 
    184, 184, 188, 195, 198, 220, 255, 275, 350, 310, 315, 320, 320, 
    316, 300, 310, 310, 320, 317, 313, 312, 310, 297, 285, 285, 286, 
    288, 315, 328, 338, 344, 345, 352, 352, 342, 335, 343, 340, 342, 
    339, 337, 336, 336, 342, 347, 352, 352, 351, 352, 352, 351, 352, 
    352, 355, 375, 400, 452, 487, 476, 475, 473, 485, 500, 530, 595, 
    720, 720, 770, 750, 770, 750, 735, 740, 745, 735, 700, 700, 750, 
    760, 755, 755, 760, 760, 765, 950, 950, 950, 875, 875, 875, 880, 
    880, 880, 900, 900, 900, 880, 880, 890, 895, 890, 880, 870, 870, 
    870, 870, 870, 860, 860, 860, 860, 850, 840, 810, 820, 810, 810, 
    805, 810, 805, 820, 815, 820, 805, 790, 800, 780, 760, 765, 750, 
    740, 820, 810, 800, 800, 775, 750, 810, 750, 740, 700, 705, 660, 
    630, 640, 595, 590, 570, 565, 535, 440, 400, 410, 400, 405, 390, 
    370, 300, 300, 180, 200, 310, 290, 260, 260, 275, 260, 270, 265, 
    255, 250, 210, 210, 200, 195, 210, 215, 240, 240, 220, 220, 220, 
    220, 210, 212, 208, 220, 210, 212, 208, 220, 215, 220, 214, 214, 
    213, 212, 210, 210, 195, 195, 160, 160, 175, 205, 210, 208, 197, 
    181, 185)), .Names = c("Date", "value"), row.names = c(NA, 393L
    ), class = "data.frame")

解决方案

The code below provides two potential options for adding year labels.

Option 1a: Faceting

You could use faceting to mark the years. For example:

library(ggplot2)
library(lubridate)

ggplot(df, aes(Date, value)) +
  geom_line() +
  scale_x_date(date_labels="%b", date_breaks="month", expand=c(0,0)) +
  facet_grid(~ year(Date), space="free_x", scales="free_x", switch="x") +
  theme_bw() +
  theme(strip.placement = "outside",
        strip.background = element_rect(fill=NA,colour="grey50"),
        panel.spacing=unit(0,"cm"))

Note that with this approach, if there are missing dates at the beginning or end of a year (by "missing", I mean rows for those dates are not even present in the data) then the x-axis will start/end at the first/last date in the data for that year, rather than go from Jan-1 to Dec-31. In that case, you'd need to add in rows for the missing dates and either NA for value or interpolate value. In addition, with this method there is no space or line between December 31 of one year and January 1 of the next year, so there's a discontinuity across each year.

Option 1b: Faceting + centered month labels

To address @AF7's comment. You can center the month labels by adding some spaces before each label. But you have to choose the number of spaces manually, depending on the physical size of the plot when you print it to a device. (There's probably a way to center the labels programmatically based on the internal grob measurements, but I'm not sure how to do it.) I've also removed the minor vertical gridlines and lightened the line between years.

ggplot(df, aes(Date, value)) +
  geom_line() +
  scale_x_date(date_labels=paste(c(rep(" ",11), "%b"), collapse=""), 
               date_breaks="month", expand=c(0,0)) +
  facet_grid(~ year(Date), space="free_x", scales="free_x", switch="x") +
  theme_bw() +
  theme(strip.placement = "outside",
        strip.background = element_blank(),
        panel.grid.minor.x = element_blank(),
        panel.border = element_rect(colour="grey70"),
        panel.spacing=unit(0,"cm"))

Option 2a: Edit the x-axis label grob

Here's a more complex and finicky method (though it could likely be automated by someone who understands the structure and unit spacings of grid graphics better than I do) that avoids the pitfalls of the faceting method described above:

library(grid)

# Fake data with an extra year added for illustration
set.seed(2)
df = data.frame(Date=seq(as.Date("1718-03-01"),as.Date("1721-09-20"), by="1 day"))
df$value = cumsum(rnorm(nrow(df)))

# The plot we'll start with
p = ggplot(df, aes(Date, value)) +
  geom_vline(xintercept=as.numeric(df$Date[yday(df$Date)==1]), colour="grey60") +
  geom_line() +
  scale_x_date(date_labels="%b", date_breaks="month", expand=c(0,0)) +
  theme_bw() +
  theme(panel.grid.minor.x = element_blank()) +
  labs(x="")

Now we want to add the year values below and in between June and July of each year. The code below does that by modifying the x-axis label grob and is adapted from this SO answer by @SandyMuspratt.

# Get the grob
g <- ggplotGrob(p)

# Get the y axis
index <- which(g$layout$name == "axis-b")  # Which grob
xaxis <- g$grobs[[index]]   

# Get the ticks (labels and marks)
ticks <- xaxis$children[[2]]

# Get the labels
ticksB <- ticks$grobs[[2]]

# Edit x-axis label grob
# Find every index of Jun in the x-axis labels and add a newline and
# then a year label
junes = which(ticksB$children[[1]]$label == "Jun")
ticksB$children[[1]]$label[junes] = paste0(ticksB$children[[1]]$label[junes],
                                           "
      ", unique(year(df$Date))) 

# Put the edited labels back into the plot
ticks$grobs[[2]] <- ticksB
xaxis$children[[2]] <- ticks
g$grobs[[index]] <- xaxis

# Draw the plot
grid.newpage()
grid.draw(g)

Option 2b: Edit the x-axis label grob and center the month labels

Below is the only change that needs to be made to Option 2a to center the month labels, but, once again, the number of spaces needs to be tweaked manually.

# Make the edit
# Center the month labels between ticks
ticksB$children[[1]]$label = paste0(paste(rep(" ",7),collapse=""), ticksB$children[[1]]$label)

# Find every index of Jun in the x-axis labels and a year label
junes = grep("Jun", ticksB$children[[1]]$label)
ticksB$children[[1]]$label[junes] = paste0(ticksB$children[[1]]$label[junes], "
      ", unique(year(df$Date))) 

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