在很多作图中，我们都涉及过添加标签，例如火山图，一般都是用ggrepel中的geom_text_repel函数。
构建一个散点图。

library(ggplot2)
library(ggrepel)
setwd("C:/Users/tq199/Desktop")
A <- read.csv("A.csv", header = T)

ggplot(A, aes(x=rank, y=avg_log2FC)) + 
  geom_point(size=3, color='#DC050C')+
  theme_bw()+
  theme(panel.grid.major=element_blank(),
        panel.grid.minor=element_blank(),
        axis.title = element_text(colour = 'black', size = 15),
        axis.text = element_text(colour = 'black', size = 12))+
  labs(x='Rank', y='Log2FC')

image.png

需要标签的点整理一个单独的文件，直接使用geom_text_repel，设置下箭头、大小、字体等等。但是我们会发现一个问题，那就是有些标签不会显示（显示不全），这是因为太多导致重复了。

B <- read.csv("B.csv", header = T)

ggplot(A, aes(x=rank, y=avg_log2FC)) + 
  geom_point(size=3, color='#DC050C')+
  geom_point(data = A[abs(A$avg_log2FC)<0.5,], 
             stroke = 0.5, size=3, shape=16, color="grey50",alpha =0.4)+
  theme_bw()+
  theme(panel.grid.major=element_blank(),
        panel.grid.minor=element_blank(),
        axis.title = element_text(colour = 'black', size = 15),
        axis.text = element_text(colour = 'black', size = 12))+
  labs(x='Rank', y='Log2FC')+
  geom_text_repel(data=B, aes(label=X), color="black", size=4, fontface="italic", 
                  arrow = arrow(ends="first", length = unit(0.01, "npc")), box.padding = 0.2,
                  point.padding = 0.3, segment.color = 'black', segment.size = 0.3, force = 1, max.iter = 3e3)

image.png

在很多文章中，我们发现别人的标签排列很整齐，这里只需要设置两个小参数即可。第一direction设置y轴对齐，nudge_x设置指示线长一点即可。

B1 <- B[B$avg_log2FC>0,]
B2 <- B[B$avg_log2FC<0,]


ggplot(A, aes(x=rank, y=avg_log2FC)) + 
  geom_point(size=3, color='#DC050C')+
  geom_point(data = A[abs(A$avg_log2FC)<0.5,], 
             stroke = 0.5, size=3, shape=16, color="grey50",alpha =0.4)+
  theme_bw()+
  theme(panel.grid.major=element_blank(),
        panel.grid.minor=element_blank(),
        axis.title = element_text(colour = 'black', size = 15),
        axis.text = element_text(colour = 'black', size = 12))+
  labs(x='Rank', y='Log2FC')+
  geom_text_repel(data=B1, aes(label=X), color="black", size=4, fontface="italic", 
                  size=3, segment.size=0.5, nudge_x=500, direction="y", hjust=0)+
  geom_text_repel(data=B2, aes(label=X), color="black", size=4, fontface="italic", 
                 size=3, segment.size=0.5, nudge_x=-1000, direction="y", hjust=0)

图片

最后，如果需要标注的点比较散，也可以使用x对齐。

B3 <- B2[abs(B2$avg_log2FC)>1.2,]
ggplot(A, aes(x=rank, y=avg_log2FC)) + 
  geom_point(size=3, color='#DC050C')+
  geom_point(data = A[abs(A$avg_log2FC)<0.5,], 
             stroke = 0.5, size=3, shape=16, color="grey50",alpha =0.4)+
  theme_bw()+
  theme(panel.grid.major=element_blank(),
        panel.grid.minor=element_blank(),
        axis.title = element_text(colour = 'black', size = 15),
        axis.text = element_text(colour = 'black', size = 12))+
  labs(x='Rank', y='Log2FC')+
  geom_text_repel(data=B3, aes(label=X), color="black", size=4, fontface="italic", 
                  size=3, segment.size=0.5, nudge_x=-1000, direction="x", hjust=0)

参数

大部分geom_text()的参数都适用于geom_text_repel(),除了以下几个：

hjust
vjust
position
check_overlap

ggrepel包为geom_text_repel()与geom_label_repel()提供了特有的参数设置：

segment.color:连接点与标签的线段的颜色
segment.size:线段的粗细
segment.alpha:线段的透明度
box.padding:文本框周边填充
point.padding:点周围填充
arrow:grid:arrow提供的箭头
force:强制性将重叠文本散开
max.oter:最大迭代次数
nudge_x/y:标签开始位置在坐标轴的移动距离
direction:允许标签的方向，x、y or both

下面举个栗子来详细了解这些参数的图形效果

set.seed(42)
ggplot(mtcars)+ geom_point(aes(wt, mpg, color=factor(cyl)), size=3)+
geom_text_repel(aes(wt, mpg, color=factor(cyl),
label=rownames(mtcars), angle=ifelse(mtcars$cyl==4, 90, 0)),
size=4, family="Times", fontface="bold",
box.padding=unit(0.5, "lines"), point.padding=unit(1.6, "lines"),
segment.color = "#cccccc", segment.size = 0.5,
arrow = arrow(length=unit(0.01, "npc")),force = 1, max.iter = 3e3,
nudge_x = ifelse(mtcars$cyl==6, 2, 0), nudge_y = ifelse(mtcars$cyl==6, 9, 0))+
scale_color_discrete(name="cyl")+
scale_x_continuous(expand = c(0.5, 0))+
scale_y_continuous(expand = c(0.25, 0))+
theme_classic(base_size = 16)

image.png

参考
ggplot文字标签设置（geom_text_repel函数）的一个小例子
R语言可视化学习笔记之ggrepel包