library(tidyverse)

21.2标签

1、labs()

ggplot(mpg,aes(displ,hwy))+
  geom_point(aes(color=class))+
  geom_smooth(se=F)+
  labs(
    title = paste(
      "Fuel efficiency generally decreases with",
      "engine size"
    )
  )

image.png

使用图形标题的目的是概括主要成果，尽量不要使用只对图形进行描述的标题

2、subtitle——在标题以下用更小的字体添加更多附加信息

3、caption——可以在图形右下角添加文本，常用于描述数据来源

ggplot(mpg,aes(displ,hwy))+
  geom_point(aes(color=class))+
  geom_smooth(se=F)+
  labs(
    title = paste(
      "Fuel efficiency generally decreases with",
      "engine size"
    ),
    subtitle = paste(
      "Two seaters(sports cars) are an exception",
      "because of their light weight"
    ),
    caption = "Data from fueleconomy.gov"
  )

image.png

(这里"，”使用的位置和书上不一样，我也不知道为啥，反正能跑就行(●'◡'●)

坐标轴和图例的标题

> ggplot(mpg,aes(displ,hwy))+
+   geom_point(aes(color=class))+
+   geom_smooth(se=F)+
+   labs(
+     x = "Engine displacement (L)",
+     y = "Highway fuel economy(mpg)",
+     color = "Car Type"
+   )

image.png

用数学公式替代文本

• quote() ← ""
• ？plotmath()查看可用选项

df <- tibble(
  x= runif(10),
  y= runif(10)
)
ggplot(df,aes(x,y))+
  geom_point()+
  labs(
    x=quote(sum(x[i]^2,i=1,n)),
    y=quote(alpha+beta +frac(delta,theta))
  )

image.png

21.3 注释

• 选取每类汽车中效率最高的型号，然后再图形中标记出来

> best_in_class <- mpg %>% 
+   group_by(class) %>% 
+   filter(row_number(desc(hwy))==1)
> 
> ggplot(mpg,aes(displ,hwy))+
+   geom_point(aes(color=class))+
+   geom_text(aes(label=model),data = best_in_class)

image.png

标签和点彼此重叠，解决方案：换用geom_label(0

使用geom_label()函数

> ggplot(mpg,aes(displ,hwy))+
+   geom_point(aes(color=class))+
+   geom_label(
+     aes(label=model),
+     data = best_in_class,
+     nudge_y = 2,
+     alpha=1/2
+   )

image.png

左上角有两个标签完全重叠，可以使用ggrepel包

使用ggrepel包——可以自动调整标签位置避免重叠

> library(ggrepel)
> library(ggrepel)
> ggplot(mpg,aes(displ,hwy))+
+   geom_point(aes(color=class))+
+   #添加图层标识best
+   geom_point(size=3,shape=1,data = best_in_class)+
+   geom_label_repel(
+     aes(label=model),
+     data = best_in_class
+   )

image.png

> class_avg <-  mpg %>% 
+   group_by(class) %>% 
+   summarise(
+     displ=median(displ),
+     hwy = median(hwy)
+   )
`summarise()` ungrouping output (override with `.groups` argument)
> class_avg
# A tibble: 7 x 3
  class      displ   hwy
  <chr>      <dbl> <dbl>
1 2seater     6.2   25  
2 compact     2.2   27  
3 midsize     2.8   27  
4 minivan     3.3   23  
5 pickup      4.7   17  
6 subcompact  2.2   26  
7 suv         4.65  17.5

> ggplot(mpg,aes(displ,hwy,color=class))+
+   geom_label_repel(aes(label=class),
+                    data = class_avg,
+                    size=2,
+                    label.size = 1,
+                    segment.color = NA)+
+   geom_point()+
+   theme(legend.position = "none")

image.png

> ggplot(mpg,aes(displ,hwy,color=class))+
+   geom_label_repel(aes(label=class),
+                    data = class_avg,
+                    size=6,
+                    label.size = NA,
+                    fill= NA,
+                    segment.color = NA)+
+   geom_point()+
+   theme(legend.position = "none")

image.png

(lll￢ω￢)书上的代码再次无用……将label.size设为0并没有什么用，设为NA可，此时底色为白色；将fill设为NA，则无填充色

添加唯一的标签将其放在图片的角落

summarize（）函数计算处x和y的最大值

> label <-  mpg %>% 
+   summarise(
+     displ= max(displ),
+     hwy =max(hwy),
+     label="Increasing engine size is \nrelated to decreasing fuel economy"
+   )
> ggplot(mpg,aes(displ,hwy))+
+   geom_point()+
+   geom_text(
+     aes(label=label),
+     data = label,
+     vjust= "top",
+     hjust="right"
+   )

image.png

用+Inf/-Inf使标签紧贴图形边界而无须从数据集计算位置

l> label <-  tibble(
+   displ= Inf,
+   hwy = Inf,
+   label=paste("Increasing engine size is \nrelated to",
+   "decreasing fuel economy"
+ ))
> label
# A tibble: 1 x 3
  displ   hwy label                                                           
  <dbl> <dbl> <chr>                                                           
1   Inf   Inf "Increasing engine size is \nrelated to decreasing fuel economy"
> label <-  tibble(
+   displ= Inf,
+   hwy = Inf,
+   label=paste("Increasing engine size is \nrelated to",
+   "decreasing fuel economy"
+ ))
> 
> 
> ggplot(mpg,aes(displ,hwy))+
+   geom_point()+
+   geom_text(
+     aes(label=label),
+     data = label,
+     vjust= "top",
+     hjust="right"
+   )

image.png

文本换行

• stringr::str_wrap()

> "Increasing engine size is related to decreasing fuel economy." %>% 
+   stringr::str_wrap(width = 40) %>% 
+   writeLines()
Increasing engine size is related to
decreasing fuel economy.

• \n

> "Increasing engine size is \nrelated to decreasing fuel economy." %>% 
+   writeLines()
Increasing engine size is 
related to decreasing fuel economy.

标签的对齐方式

• hjust="left"/"center"/"right"
• vjust="top"/"center"/"bottom"

其他注释