r ggplot2 facet_grid如何在圖表頂部和邊框之間添加空間

Question

有沒有一種方法可以使用ggplot的facet_grid在圖表頂部的標簽和圖表的邊距之間添加空間。 以下是可重現的示例。

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)

生成的圖表在圖的邊框旁邊有數字標簽。

Answer 1

我想添加到@dww的答案中，但沒有足夠的聲譽。

實際上， expand選項將允許您僅在圖形頂部添加空間。 從?expand_scale幫助文件中：

# 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

一種簡單的方法是使用scale_y_continuous的expand參數：

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的缺點是，它將在條形圖的上方和下方添加空間。 一種替代方法是在條形圖上方的高度上在圖形上繪制一些不可見數據，這將迫使ggplt擴展軸范圍以適應該虛擬數據。 在這里，我添加了一些不可見的條形，其高度為實際條形的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)