r ggplot2 facet_grid如何在图表顶部和边框之间添加空间

Question

有没有一种方法可以使用ggplot的facet_grid在图表顶部的标签和图表的边距之间添加空间。 以下是可重现的示例。

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)

生成的图表在图的边框旁边有数字标签。

Answer 1

我想添加到@dww的答案中，但没有足够的声誉。

实际上， expand选项将允许您仅在图形顶部添加空间。 从?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，它将在条形图的上方和下方添加空间。 一种替代方法是在条形图上方的高度上在图形上绘制一些不可见数据，这将迫使ggplt扩展轴范围以适应该虚拟数据。 在这里，我添加了一些不可见的条形，其高度为实际条形的1.2 *：

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)