r ggplot2 facet_grid如何在图表顶部和边框之间添加空格

Question

有没有办法在图表顶部的标签和使用ggplot的facet_grid绘图的边距之间添加空格。以下是一个可重复的例子。

library(dplyr)
library(ggplot2)
Titanic %>% as.data.frame() %>%
filter(Survived == "Yes") %>% 
mutate(FreqSurvived = ifelse(Freq > 100, Freq*1e+04,Freq)) %>%
ggplot( aes(x = Age, y = FreqSurvived, fill = Sex)) +
geom_bar(stat = "identity", position = "dodge") +
facet_grid(Class ~ ., scales = "free") +
theme_bw() +
geom_text(aes(label = prettyNum(FreqSurvived,big.mark = ",")), vjust = 0, position = position_dodge(0.9), size = 2)

生成的图表在图表边框旁边有数字标签。

Answer 1

我想添加到@dww的答案中，但是声誉不够。

expand选项实际上将允许您仅在图形顶部添加空间。在?expand_scale帮助文件中：

# No space below the bars but 10% above them
ggplot(mtcars) +
  geom_bar(aes(x = factor(cyl))) +
  scale_y_continuous(expand = expand_scale(mult = c(0, .1)))

Answer 2

一种简单的方法是使用scale_y_continuous的expand参数：

dt = Titanic %>% as.data.frame() %>%
  filter(Survived == "Yes") %>% 
  mutate(FreqSurvived = ifelse(Freq > 100, Freq*1e+04,Freq))

ggplot(dt, aes(x = Age, y = FreqSurvived, fill = Sex)) +
  geom_bar(stat = "identity", position = "dodge") +
  facet_grid(Class ~ ., scales = "free") +
  theme_bw() +
  geom_text(aes(label = prettyNum(FreqSurvived,big.mark = ",")), 
            vjust = 0, position = position_dodge(0.9), size = 2) +
  scale_y_continuous(expand = c(0.1,0))

使用expand的缺点是它会在条形图的上方和下方添加空间。另一种方法是在条形图上方的高度处绘制一些不可见数据，这将迫使ggplt扩展轴范围以容纳这些虚拟数据。在这里，我添加了一些不可见的条形，其高度为1.2 *实际条形：

Titanic %>% as.data.frame() %>%
  filter(Survived == "Yes") %>% 
  mutate(FreqSurvived = ifelse(Freq > 100, Freq*1e+04,Freq)) %>%
  ggplot( aes(x = Age, y = FreqSurvived, fill = Sex)) +
  geom_bar(aes(y = FreqSurvived*1.2), stat = "identity", 
           position = "dodge", fill=NA) +
  geom_bar(stat = "identity", position = "dodge") +
  facet_grid(Class ~ ., scales = "free") +
  theme_bw() +
  geom_text(aes(label = prettyNum(FreqSurvived,big.mark = ",")), 
            vjust = 0, 
            position = position_dodge(0.9), size = 2)