R中具有ggtext和gridtext的R中具有跨图图例的多面板图

正确的方法是使用plot_annotation()。字幕两侧各有一些水平间隙的原因是，与常规ggplot2一样，绘图边距仍应用于字幕。如果要避免这种情况，则必须将绘图边距设置为0，并通过在轴标题等中添加适当的边距来创建间距。

# Library calls
library(tidyverse)
library(ggtext)
library(patchwork)

# make dummy figures
d1 <- runif(500)
d2 <- rep(c("Treatment", "Control"), each=250)
d3 <- rbeta(500, shape1=100, shape2=3)
d4 <- d3 + rnorm(500, mean=0, sd=0.1)
plotData <- data.frame(d1, d2, d3, d4)

p1 <- ggplot(data=plotData) + geom_point(aes(x=d3, y=d4)) +
  theme(plot.background = element_rect(color='black'))
p2 <- ggplot(data=plotData) + geom_boxplot(aes(x=d2, y=d1, fill=d2))+
  theme(legend.position="none") +
  theme(plot.background = element_rect(color='black'))
p3 <- ggplot(data=plotData) +
  geom_histogram(aes(x=d1, color=I("black"), fill=I("orchid"))) +
  theme(plot.background = element_rect(color='black'))
p4 <- ggplot(data=plotData) +
  geom_histogram(aes(x=d3, color=I("black"), fill=I("goldenrod"))) +
  theme(plot.background = element_rect(color='black'))


fig_legend <- plot_annotation(
  caption = "**Figure 1.**  Testing Control vs. Treatment.   A. Scatterplot. 
  B. The outcomes in the control arm were significantly better than 
  the Treatment Arm. C. Histogram. D. Another Histogram.",
  theme = theme(
    plot.caption = element_textbox_simple(
      size = 11,
      box.colour = "black",
      linetype = 1,
      padding = unit(c(3, 3, 3, 3), "pt"),
      r = unit(0, "pt")
    )
  )
)


p1 + {
  p2 + {
    p3 +
      p4 +
      plot_layout(ncol=1)
  }
} + fig_legend +
  plot_layout(ncol=1)
#> `stat_bin()` using `bins = 30`. Pick better value with `binwidth`.
#> `stat_bin()` using `bins = 30`. Pick better value with `binwidth`.

^{由reprex软件包（v0.3.0）创建于2020-02-09}

实际上，您可以在标题上使用负边距来抵消绘图边距。

fig_legend <- plot_annotation(
  caption = "**Figure 1.**  Testing Control vs. Treatment.   A. Scatterplot. 
  B. The outcomes in the control arm were significantly better than 
  the Treatment Arm. C. Histogram. D. Another Histogram.",
  theme = theme(
    plot.caption = element_textbox_simple(
      size = 11,
      box.colour = "black",
      linetype = 1,
      padding = unit(c(3, 3, 3, 3), "pt"),
      margin = unit(c(0, -5.5, 0, -5.5), "pt"),
      r = unit(0, "pt")
    )
  )
)


p1 + {
  p2 + {
    p3 +
      p4 +
      plot_layout(ncol=1)
  }
} + fig_legend +
  plot_layout(ncol=1)
#> `stat_bin()` using `bins = 30`. Pick better value with `binwidth`.
#> `stat_bin()` using `bins = 30`. Pick better value with `binwidth`.

^{由reprex软件包（v0.3.0）创建于2020-02-09}