r - 如何将ggplot图标题居中

Question

在 ggplot 中居中对齐绘图标题的“lege artis”方式 - plot.title = element_text(hjust = 0.5) - 将标题置于绘图区域的中心不包括轴标签。

当轴标签很长时，这可能会变得很难看，例如《欢乐满人间》原声带中的歌曲与字符长度的关系图。

library(tidyverse)

mary_poppins <- data_frame(song = c("Overture", "Sister Suffragette", "The Life I Lead", "The Perfect Nanny", "A Spoonful of Sugar", "Pavement Artist", "Jolly Holiday", "Supercalifragilisticexpialidocious", "Stay Awake", "I Love to Laugh", "A British Bank", "Feed the Birds ", "Fidelity Fiduciary Bank", "Chim Chim Cher-ee", "Step in Time", "A Man Has Dreams", "Let's Go Fly a Kite"
))

mary_poppins <- mary_poppins %>%
  mutate(len = nchar(song))

ggplot(data = mary_poppins, aes(x = reorder(song, len), y = len)) +
  geom_col(fill = "firebrick") +
  coord_flip() +
  theme_light() +
  theme(axis.title.y = element_blank(),
        axis.text = element_text(size = rel(1.5)),
        plot.title = element_text(size = rel(2.5), face = "bold", hjust = 0.5, 
                                  margin = margin(t = 10, b = 20, unit = "pt"))) +
  ggtitle("Mary Poppins") +
  ylab("Lenght of title (characters)")

有没有办法将标题置于整个绘图区域的中心，即包括轴标签占据的区域？

Answer 1

解决该问题的一个简单方法是将以下内容添加到图中:

theme(plot.title.position = 'plot', 
      plot.title = element_text(hjust = 0.5))

第一部分告诉ggplot使用整个绘图作为居中的引用，第二部分使标题居中。