ggplot2 多行标题，不同的缩进

Question

我正在为出版物生成图表，我希望能够在 ggplot 本身中标记图形的面板（而不是导出到发布者等），以便它们在最终的结果中整齐地组合在一起文档。我打算通过在标题中添加一个字母 ("A") 来尝试做到这一点，但我希望我的标题居中并且我想要左上角的字母。

# base graph:

ggplot(iris, aes(x = Sepal.Length, y = Sepal.Width, color = Species, shape = Species))+
  geom_jitter(size = 6.5)+
  ggtitle("A \n \n The Actual Long, Normal Title of Titliness")+
  theme(plot.title = element_text(hjust = 0.5, face = "bold", size = 30),
        axis.ticks = element_blank(),
        legend.text = element_text(size = 25),
        axis.title = element_text(size = 25, face = "bold"),
        axis.text = element_text(size = 25, vjust = 0.05),
        legend.position = "bottom")

现在，如果我愿意 "fake it" 通过 hand-spacing 每个标题，我可以让它发挥作用，但这似乎很费时间而且很粗糙。

# sloppy solution
ggplot(iris, aes(x = Sepal.Length, y = Sepal.Width, color = Species, shape = Species))+
  geom_jitter(size = 6.5)+
  ggtitle("A \n \n             The Actual Long, Normal Title of Titliness")+
  theme(plot.title = element_text(hjust = 0,face = "bold", size = 30),
        axis.ticks = element_blank(),
        legend.text = element_text(size = 25),
        axis.title = element_text(size = 25, face = "bold"),
        axis.text = element_text(size = 25, vjust = 0.05),
        legend.position = "bottom")

有没有办法单独调用标题的每个 'line' 以获得它自己的 hjust 值？

还有其他创造性的解决方案吗？

此外，我在 mtext (Splitting axis labels with expressions) 中看到了潜力，但无法弄清楚如何使用 ggplot2 来实现它（与基本绘图功能相比……似乎它们不兼容）。这个 post 很有趣 ()，但我对 R 还是个新手，我不知道如何编辑这个聪明的东西来改变缩进.

谢谢！

Answer 1

您可以使用包 grid 中的 grid.text，将文本添加到您的绘图中。首先在标题上方添加一些 space 使用 plot.margin.

library(grid)
p <- ggplot(iris, aes(x = Sepal.Length, y = Sepal.Width, color = Species, shape = Species))+
geom_jitter(size = 6.5)+
ggtitle("The Actual Long, Normal Title of Titliness")+
theme(plot.title = element_text(hjust = 0,face = "bold", size = 30),
      axis.ticks = element_blank(),
      legend.text = element_text(size = 25),
      axis.title = element_text(size = 25, face = "bold"),
      axis.text = element_text(size = 25, vjust = 0.05),
      legend.position = "bottom", 
      plot.margin = unit(c(4, 3, 1, 1), "lines"))
p
grid.text('A', x = unit(0.1, 'npc'), y = unit(.90, 'npc'), gp = gpar(fontsize=28))

Answer 2

最简单的方法可能是使用标题和副标题，

ggplot(iris, aes(x = Sepal.Length, y = Sepal.Width, color = Species, shape = Species))+
  geom_jitter(size = 6.5) +
  labs(title = "A", subtitle = "The Actual Long, Normal Title of Titliness") +
  theme(plot.subtitle = element_text(hjust = 0.5))

Answer 3

你可以通过操纵 Grobs 来做到这一点。在 ggplot2.

之上使用 gtable 和 grid

library("ggplot2")
library("gtable")
library("grid")

p <- ggplot(iris, aes(x = Sepal.Length, y = Sepal.Width, color = Species, shape = Species))+
  geom_jitter(size = 6.5)+
  ggtitle("The Actual Long, Normal Title of Titliness")+
  theme(plot.title = element_text(hjust = 0.5, face = "bold", size = 30),
        axis.ticks = element_blank(),
        legend.text = element_text(size = 25),
        axis.title = element_text(size = 25, face = "bold"),
        axis.text = element_text(size = 25, vjust = 0.05),
        legend.position = "bottom",
        plot.margin = unit(c(4, 1, 1, 4), "lines"))  # We need bigger top/left margins to show the letter

gt <- ggplot_gtable(ggplot_build(p))  # Building a gtable from the ggplot object
# Adding the textGrob for the panel letter
panel_letter = textGrob("A", x = 0.5, y = .9, 
                        just = c("left", "top"), 
                        gp = gpar(fontsize = 40, col =  "black", face="bold"))
gt <- gtable_add_grob(gt, panel_letter, t=1, l=1, r=1)  # Append the Grob to the table

p <- grid.draw(gt)  # Display the plot
ggsave("plot.png",gt, width=10, height=10)  # If you want to save it.

Answer 4

更新：从 ggplot2 3.0.0 开始，现在原生支持绘图标签，

这是我的做法，使用我专门为此目的编写的 cowplot 包。请注意，您会得到一个干净的主题作为奖励。

library(cowplot)

p <- ggplot(iris, aes(x = Sepal.Length, y = Sepal.Width, color = Species, shape = Species)) +
  geom_jitter(size = 3.5) +
  ggtitle("The Actual Long, Normal Title of Titliness")

# add one label to one plot
ggdraw(p) + draw_plot_label("A")

# place multiple plots into a grid, with labels
plot_grid(p, p, p, p, labels = "AUTO")

然后您想要使用 save_plot 函数而不是 ggsave 来保存绘图，因为 save_plot 具有默认值和参数，可帮助您获得相对于主题的正确缩放比例，特别是对于网格中的图。

Answer 5

因为 ggplot2 3.0.0, there is a native way to do this, using the tag label:

ggplot(iris, aes(x = Sepal.Length, y = Sepal.Width, color = Species, shape = Species)) +
  geom_point() +
  labs(title = "The Actual Long, Normal Title of Titliness",
       tag = "A")

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