如何修改ggMarginal背景色以匹配ggplot主图背景？

使用ggExtra::ggMarginal()为ggplot添加侧边密度直方图时，边际图默认背景为白色，无法匹配主图设置的#fffdf7背景色，导致图表衔接处出现白色线条。以下是修复方案：

核心修改点 #

直接在ggMarginal()中通过theme参数传递与主图一致的背景色设置，覆盖默认主题的白色背景。

修改后的完整代码 #

library(tidyverse)
library(readxl)
library(summarytools)
library(ggExtra)
library(ggtext)

tr <- ggplot(mtcars) +
  aes(x = mpg, y = disp, color = as.character(cyl), shape = as.character(cyl)) +
  geom_point(size = 3) +
  geom_smooth(method = "lm",
              se = TRUE,
              show.legend = FALSE,
              alpha = 0.1) +
  scale_color_manual(values = c("#325756FF", "#7D9FC2FF", "#C582B2FF", "#51806AFF", "#4D5F8EFF", "#A092B7FF")) +
  labs(
    title = "<i> Mtcars</i> Vizualization Project",
    subtitle = "Model for <b style='color:#325756FF'>4</b>, <b style='color:#7D9FC2FF'>6</b>, and <b style='color:#C582B2FF'>8</b> Cylinders",
    x = "MPG",
    y = "Dispersion",
    caption = "Sources: mtcars.",
    shape = "Cylinder",
    color = "Cylinder",
    fill = "Cylinder"
  ) +
  theme(
    legend.position = "bottom",
    legend.title = element_text(
      family = "",
      face = "bold",
      size = 16,
      color = "grey30"
    ),
    legend.background = element_blank(),
    legend.box.background = element_blank(),
    legend.key = element_blank(),
    text = element_text(
      family = "",
      face = "bold",
      size = 16,
      color = "grey30"
    ),
    plot.title = element_markdown(
      lineheight = 1.1,
      family = "",
      size = 20,
      face = "bold",
      hjust = 0.5,
      color = "grey30"
    ),
    plot.subtitle = element_markdown(
      family = "",
      size = 14,
      hjust = 0.5,
      face = "plain",
      color = "grey30"
    ),
    plot.caption = element_text(
      family = "",
      size = 10,
      face = "plain",
      color = "grey30"
    ),
    axis.text.x = element_text(
      angle = 0, 
      face = "bold"
      ),
    axis.text.y = element_text(
      angle = 0, 
      face = "bold"
      ),
    axis.ticks = element_blank(),
    axis.line = element_line(
      color = "#b4aea9"
      ),
    panel.grid = element_line(
      color = "grey95"
      ),
    panel.grid.minor = element_blank(),
    panel.grid.major = element_line(
      linetype = "solid"
      ),
    panel.background = element_rect(
      fill = "#fffdf7", 
      color = "#fffdf7"
      ),
    plot.background = element_rect(
      fill = "#fffdf7", 
      color = "#fffdf7"
      )
  )

# 修改ggMarginal部分，添加theme参数匹配主图背景
tr %>% 
  ggMarginal(
    groupColour = TRUE,
    groupFill = TRUE,
    # 传递自定义主题给边际图
    theme = theme(
      panel.background = element_rect(fill = "#fffdf7", color = "#fffdf7"),
      plot.background = element_rect(fill = "#fffdf7", color = "#fffdf7"),
      # 可选：保持边际图的轴文本样式与主图一致
      axis.text = element_text(face = "bold", color = "grey30"),
      axis.ticks = element_blank()
    )
  )

说明 #

ggMarginal()默认使用ggplot的基础主题（白色背景），因此需要显式传递与主图完全一致的背景色设置。通过在ggMarginal的theme参数中指定panel.background和plot.background的填充色为#fffdf7，即可消除主图与边际图之间的白色衔接线条，实现整体背景统一。

内容的提问来源于stack exchange，提问作者M.Frumh