对齐水平ggplot条形图的标题，副标题和标题

Question

我想在水平 ggplot2 条形图中左对齐 plot.title、plot.subtitle 和 plot.caption。

例子：

library("ggplot2") # ggplot2 2.2
df <- data.frame(type=factor(c("Brooklyn",
                               "Manhatten and\n Queens")),
                 value=c(15,30))

# manual hjust for title, subtitle & caption
myhjust <- -0.2

ggplot(df,
       aes(x=type, y=value)) +
  geom_bar(stat='identity') +
  coord_flip() +
  labs(
    title = "This is a nice title",
    subtitle = "A subtitle",
    caption  = "We even have a caption. A very long one indeed.") +
  theme(axis.title=element_blank(),
        plot.title=element_text(hjust = myhjust),
        plot.subtitle=element_text(hjust = myhjust ),
        plot.caption=element_text(hjust = myhjust))

如何将所有 3 个 labs 元素（plot.title、plot.subtitle 和 plot.caption）与 axis.text 的开始位置（红色垂直线，Manhatten 的“M”）对齐？

另外：为什么固定的myhjust 会导致plot.title、plot.subtitle 和plot.caption 出现3 个不同的水平位置？

Answer 1

这个问题是指这个 github tidyverse/ggplot2 解决的问题：https://github.com/tidyverse/ggplot2/issues/3252

并且在ggplot2（开发版）中实现：https://github.com/tidyverse/ggplot2/blob/15263f7580d6b5100989f7c1da5d2f5255e480f9/NEWS.md

主题获得了两个新参数 plot.title.position 和 plot.caption.position，可用于自定义情节标题/副标题和情节标题相对于整体情节的定位方式（@clauswilke，#3252） .

以您的榜样为代表：

# First install the development version from GitHub:
#install.packages("devtools") #If required
#devtools::install_github("tidyverse/ggplot2")

library(ggplot2)
packageVersion("ggplot2")
#> [1] '3.2.1.9000'

df <- data.frame(type=factor(c("Brooklyn","Manhatten and\n Queens")),
                 value=c(15,30))

ggplot(df, aes(x=type, y=value)) +
  geom_bar(stat='identity') +
  coord_flip() +
  labs(title = "This is a nice title",
       subtitle = "A subtitle",
       caption  = "We even have a caption. A very long one indeed.") +
  theme(plot.caption = element_text(hjust = 0, face= "italic"), #Default is hjust=1
        plot.title.position = "plot", #NEW parameter. Apply for subtitle too.
        plot.caption.position =  "plot") #NEW parameter

^{由reprex package (v0.3.0) 于 2019 年 9 月 4 日创建}

Answer 2

虽然您可以编辑这三个 grobs，但您也可以：

library(gridExtra)
library(grid)

grid.arrange(
  textGrob("This is a nice title", 
           gp=gpar(fontsize=16, col="#2b2b2b"), 
           x=unit(0.005, "npc"), just=c("left", "bottom")),
  textGrob("A subtitle",  
           gp=gpar(fontsize=12, col="#2b2b2b"), 
           x=unit(0.005, "npc"), just=c("left", "bottom")),
  ggplot(df, aes(x=type, y=value)) +
    geom_bar(stat='identity') +
    coord_flip() +
    theme(axis.title=element_blank()),
  textGrob("We even have a caption. A very long one indeed.", 
           gp=gpar(fontsize=9, col="#2b2b2b"), 
           x=unit(0.005, "npc"), just=c("left", "bottom")),
  ncol=1,
  heights=c(0.075, 0.025, 0.85, 0.05)
)

为它制作一个包装器，将其放入个人 pkg 中。繁荣。完成。

---

library(ggplot2)
library(gridExtra)
library(grid)

df <- data.frame(type=factor(c("Brooklyn","Manhatten and\n Queens")), value=c(15,30))

ggplot(df, aes(x=type, y=value)) +
  geom_bar(stat='identity') +
  coord_flip() +
  theme(axis.title=element_blank()) +
  theme(plot.margin=margin(l=0, t=5, b=5))-> gg

flush_plot <- function(x, title, subtitle, caption) {
  tg <- function(label, ...) {
    textGrob(label,  x=unit(0, "npc"), just=c("left", "bottom"),
             gp=do.call(gpar, as.list(substitute(list(...)))[-1L])) }
  grid.arrange(
    tg(title, fontsize=16, col="#2b2b2b"),
    tg(subtitle, fontsize=12, col="#2b2b2b"), x,
    tg(caption, fontsize=9, col="#2b2b2b"),
    ncol=1, heights=c(0.075, 0.025, 0.85, 0.05)
  )
}

flush_plot(gg, "This is a nice title", "A subtitle", 
           "We even have a caption. A very long one indeed.")