用额外的勾号和标签标注ggplot [英] Annotate ggplot with an extra tick and label

问题描述

你能帮我注释一张ggplot2散点图吗？

到一个典型的散点图（黑色）：

  df< ;  -  data.frame（x = seq（1：100），y = sort（rexp（100，2），decrease = T））
 ggplot（df，aes（x = x，y = y）） + geom_point（）
  

我想以额外的勾号和自定义标签的形式添加注释（红色）：

示例图像：

解决方案

四种解决方案。

第一个使用 scale_x_continuous 添加附加元素，然后使用 theme


第二个使用 annotate_custom 来自定义新的文本和刻度标记（加上一些额外的调整）。创建新的grobs：文本grob和线grob。 grobs的位置在数据坐标中。结果是如果y轴的极限改变，grob的定位将会改变。因此，下面的示例中y轴是固定的。此外， annotation_custom 正试图在绘图面板外绘制。默认情况下，打开绘图面板的裁剪。它需要被关闭。



第三个是第二个变体（并且从

第四种解决方案

已更新至ggplot2 v2.2.0

<$ p $ （ggplot2）
库（网格）
df< - data.frame（x = seq（1：100），y = ）（$）
$ b（p = ggplot（df，aes（x = x，y = y））+ geom_point（））


＃使用正则表达式搜索绘图面板
Tree = as.character（current.vpTree（））
pos = gregexpr（\\ [panel。*？ （Tree，pos））
match = gsub（^ \\ [（panel。*？）\\] $，\\1，match）＃删除方括号
downViewport（match）

#######
＃或者找到plot面板你自己
＃current.vpTree（）＃查找绘图面板
＃downViewport（panel.6-4-6-4）
#####

＃获取ggplot的x-scale的限制，包括扩展。
x.axis.limits = ggplot_build（p）$ layout $ panel_ranges [[1]] [[x.range]]

＃在plot面板中设置单位， x轴单位实际上是本地，
＃但是y轴单位实际上是npc。
pushViewport（dataViewport（yscale = c（0，1），xscale = x.axis.limits，clip =off））
grid.text（xyz，x = 30，y = -.05，just =center，gp = gpar（col =red），default.units =native）
grid.lines（x = 30，y = c（.02， - 。 02），gp = gpar（col =red，lwd = 2），default.units =native）

upViewport（0）


Can you help me annotate a ggplot2 scatterplot?

To a typical scatter plot (black):

df <- data.frame(x=seq(1:100), y=sort(rexp(100, 2), decreasing = T))
ggplot(df, aes(x=x, y=y)) + geom_point()

I want to add annotations in the form of an extra tick and a custom label (red):

Example image:

解决方案

Four solutions.

The first uses scale_x_continuous to add the additional element then uses theme to customize the new text and tick mark (plus some additional tweaking).

The second uses annotate_custom to create new grobs: a text grob, and a line grob. The locations of the grobs are in data coordinates. A consequence is that the positioning of the grob will change if the limits of y-axis changes. Hence, the y-axis is fixed in the example below. Also, annotation_custom is attempting to plot outside the plot panel. By default, clipping of the plot panel is turned on. It needs to be turned off.

The third is a variation on the second (and draws on code from here). The default coordinate system for grobs is 'npc', so position the grobs vertically during the construction of the grobs. The positioning of the grobs using annotation_custom uses data coordinates, so position the grobs horizontally in annotation_custom. Thus, unlike the second solution, the positioning of the grobs in this solution is independent of the range of the y values.

The fourth uses viewports. It sets up a more convenient unit system for locating the text and tick mark. In the x direction, the location uses data coordinates; in the y direction, the location uses "npc" coordinates. Thus, in this solution too, the positioning of the grobs is independent of the range of the y values.

First Solution

## scale_x_continuous then adjust colour for additional element 
## in the x-axis text and ticks
library(ggplot2)
df <- data.frame(x=seq(1:100), y=sort(rexp(100, 2), decreasing = T))

p = ggplot(df, aes(x=x, y=y)) + geom_point() + 
  scale_x_continuous(breaks = c(0,25,30,50,75,100), labels = c("0","25","xyz","50","75","100")) +
  theme(axis.text.x = element_text(color = c("black", "black", "red", "black", "black", "black")),
        axis.ticks.x = element_line(color = c("black", "black", "red", "black", "black", "black"),
                          size = c(.5,.5,1,.5,.5,.5)))

# y-axis to match x-axis
p = p + theme(axis.text.y = element_text(color = "black"),
        axis.ticks.y = element_line(color = "black"))

# Remove the extra grid line
p = p + theme(panel.grid.minor = element_blank(),
              panel.grid.major.x = element_line(color = c("white", "white", NA, "white", "white", "white")))
p

Second Solution

## annotation_custom then turn off clipping
library(ggplot2)
library(grid)
df <- data.frame(x=seq(1:100), y=sort(rexp(100, 2), decreasing = T))

p = ggplot(df, aes(x=x, y=y)) + geom_point() + 
 scale_y_continuous(limits = c(0, 4)) +
 annotation_custom(textGrob("xyz", gp = gpar(col = "red")), 
        xmin=30, xmax=30,ymin=-.4, ymax=-.4) +
 annotation_custom(segmentsGrob(gp = gpar(col = "red", lwd = 2)), 
        xmin=30, xmax=30,ymin=-.25, ymax=-.15)

g = ggplotGrob(p)
g$layout$clip[g$layout$name=="panel"] <- "off"
grid.draw(g)

Third Solution

library(ggplot2)
library(grid)
df <- data.frame(x=seq(1:100), y=sort(rexp(100, 2), decreasing = T))

p = ggplot(df, aes(x=x, y=y)) + geom_point() 

gtext = textGrob("xyz", y = -.05, gp = gpar(col = "red"))
gline = linesGrob(y = c(-.02, .02),  gp = gpar(col = "red", lwd = 2)) 

p = p + annotation_custom(gtext, xmin=30, xmax=30, ymin=-Inf, ymax=Inf) +
        annotation_custom(gline, xmin=30, xmax=30, ymin=-Inf, ymax=Inf)

g = ggplotGrob(p)
g$layout$clip[g$layout$name=="panel"] <- "off"
grid.draw(g)

Fourth Solution

Updated to ggplot2 v2.2.0

## Viewports
library(ggplot2)
library(grid)
df <- data.frame(x=seq(1:100), y=sort(rexp(100, 2), decreasing = T))

(p = ggplot(df, aes(x=x, y=y)) + geom_point())


# Search for the plot panel using regular expressions
Tree = as.character(current.vpTree())
pos = gregexpr("\\[panel.*?\\]", Tree)
match = unlist(regmatches(Tree, pos))
match = gsub("^\\[(panel.*?)\\]$", "\\1", match) # remove square brackets
downViewport(match)

#######
# Or find the plot panel yourself
#  current.vpTree() # Find the plot panel
#  downViewport("panel.6-4-6-4")
#####

# Get the limits of the ggplot's x-scale, including the expansion.
x.axis.limits = ggplot_build(p)$layout$panel_ranges[[1]][["x.range"]]

# Set up units in the plot panel so that the x-axis units are, in effect, "native",
# but y-axis units are, in effect, "npc".
pushViewport(dataViewport(yscale = c(0, 1), xscale = x.axis.limits, clip = "off"))
grid.text("xyz", x = 30, y = -.05, just = "center", gp = gpar(col = "red"), default.units = "native")
grid.lines(x = 30, y = c(.02, -.02), gp = gpar(col = "red", lwd = 2), default.units = "native") 

upViewport(0)

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