如何在 R 图中命名由垂直线分隔的 x 轴部分（包 ggplot2）？

Question

我用 ggplot2 创建了一个堆积面积图，并在x-axis 的某些位置添加了垂直线。

我现在想命名由这些垂直线分隔的部分。它的一个示例可能看起来像示例图中所示。也欢迎其他解决方案。 我有一个breaks (x-axis) 的向量和一个间隔名称的向量。

代码：

library(ggplot2)
d <- read.delim(...)
x_breaks = c(-3999,1,599,4076,7557,11556)

png(output, width=800, height=400)

ggplot(d, aes(x=p, y=c, group=Groups, fill=Groups)) +
geom_area(position="stack") +
opts(title="testtestest",
...) +
scale_x_continuous(expand=c(0,0), breaks=x_breaks) +
scale_y_continuous(expand=c(0,0)) +
geom_vline(xintercept=x_breaks[which(x_breaks != min(x_breaks) & x_breaks != max(x_breaks))])

dev.off()

Answer 1

没有数据，重现您的示例（您的休息等）有点困难。但以下内容应该可以帮助您入门。

一个相当简单的解决方案是使用 ggplot2 的 annotate() 函数将文本注释添加到垂直线之间的绘图面板中。

# Load packages
library (ggplot2)
library(grid)

# Some data
df = data.frame(x = 1:10, y = 1:10)

# Base plot
p <- ggplot(df, aes(x,y)) + geom_point() + 
  scale_x_continuous(limits = c(0, 11), expand = c(0,0)) +
  geom_vline(xintercept = 3) + geom_vline(xintercept = 7)

# Add the annotations
p + annotate("text", x = .5*(0+3), y = 11, label = "Part 1") +
     annotate("text", x = .5*(3+7), y = 11, label = "Part 2") +
     annotate("text", x = .5*(7+11), y = 11, label = "Part 3")

结果是：

或者就注释而言，接近您的示例图的解决方案。它使用annotation_custom() 来绘制线条并将文本放置在绘图面板之外。即使注释是在绘图面板之外绘制的，注释的位置也是根据数据坐标进行的。基础图中的底部边距被加宽，以便为注释留出空间。该解决方案需要代码来覆盖 ggplot 将绘图元素剪辑到绘图面板。

更新 opts 已弃用；改用theme。

# Base plot
p <- ggplot(df, aes(x,y)) + geom_point() + 
  scale_x_continuous(limits = c(0, 11), expand = c(0,0)) +
  geom_vline(xintercept = 3) + geom_vline(xintercept = 7) +
  theme(plot.margin = unit(c(1,1,4,1), "lines"))

# Create the text Grobs
Text1 = textGrob("Part 1")
Text2 = textGrob("Part 2")
Text3 = textGrob("Part 3")

# Add the annotations
# Segment 1
p1 = p + 
    annotation_custom(grob = linesGrob(), xmin = 0, xmax = 0, ymin = -1, ymax = -.75) +
    annotation_custom(grob = linesGrob(), xmin = 0, xmax = 3, ymin = -1, ymax = -1) +
    annotation_custom(grob = linesGrob(), xmin = 3, xmax = 3, ymin = -1, ymax = -.75) +
    annotation_custom(grob = Text1,  xmin = 0, xmax = 3, ymin = -1.25, ymax = -1.25)

# Segment 2
p1 = p1 + 
    annotation_custom(grob = linesGrob(), xmin = 3, xmax = 7, ymin = -1, ymax = -1) +
    annotation_custom(grob = linesGrob(), xmin = 7, xmax = 7, ymin = -1, ymax = -.75) +
    annotation_custom(grob = Text2,   xmin = 3, xmax = 7, ymin = -1.25, ymax = -1.25) 

# Segment 3
p1 = p1 + 
    annotation_custom(grob = linesGrob(), xmin = 7, xmax = 11, ymin = -1, ymax = -1) +
    annotation_custom(grob = linesGrob(), xmin = 11, xmax = 11, ymin = -1, ymax = -.75) +
    annotation_custom(grob = Text3,  xmin = 7, xmax = 11, ymin = -1.25, ymax = -1.25)

# Code to override clipping
gt <- ggplot_gtable(ggplot_build(p1))
gt$layout$clip[gt$layout$name=="panel"] <- "off"
grid.draw(gt)

结果是：