ggplot2绘制条形图时为指定条形或组添加自定义边框的方法咨询

需求说明 #

使用ggplot2绘制条形图时需要实现两类边框效果：

• 单个条形仅左侧、顶部、右侧三边显示外边框
• 整组聚集条形整体添加外边框

测试数据 #

df <- structure(list(bar = c(17.5, 27.5, 32.5, 37.5, 42.5, 47.5, 52.5, 
57.5, 62.5, 67.5, 72.5, 77.5, 82.5), num = c(1L, 7L, 8L, 11L, 
22L, 46L, 43L, 60L, 59L, 40L, 17L, 11L, 1L), group = structure(c(1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L), .Label = "A", class = "factor")), class = "data.frame", row.names = c(NA, 
-13L))

初始问题代码 #

library(ggplot2)
ggplot(df, aes(bar,num, fill = group)) +
  geom_bar(stat = 'identity', width = 5) +
  scale_fill_manual(values = alpha(c("blue"), .3))

上述代码仅能生成无自定义边框的基础条形图，无法实现指定的多类边框效果。 #

可实现需求的完整代码 #

通过手动绘制线段实现单个条形三边边框，再叠加整组外框图层即可实现需求：

library(ggplot2)
# 预定义条形宽度，计算每个条形的位置边界
bar_width <- 5
df <- transform(df,
                x_left = bar - bar_width/2,
                x_right = bar + bar_width/2,
                y_top = num,
                y_bottom = 0)

ggplot(df, aes(x = bar, y = num)) +
  # 基础条形图层
  geom_col(aes(fill = group), width = bar_width) +
  scale_fill_manual(values = alpha(c("blue"), 0.3)) +
  # 绘制单个条形的三边边框
  geom_segment(aes(x = x_left, xend = x_left, y = y_bottom, yend = y_top)) + # 左侧边框
  geom_segment(aes(x = x_right, xend = x_right, y = y_bottom, yend = y_top)) + # 右侧边框
  geom_segment(aes(x = x_left, xend = x_right, y = y_top, yend = y_top)) + # 顶部边框
  # 绘制整组条形的外边框
  annotate("rect", 
           xmin = min(df$x_left), xmax = max(df$x_right),
           ymin = 0, ymax = max(df$y_top),
           color = "black", fill = NA, linewidth = 1) +
  # 可选优化：调整主题适配边框显示
  theme_bw()

效果说明 #

上述代码运行后可同时实现两类边框需求：

1. 每个独立条形仅显示左、上、右三个方向的边框，底部无边框
2. 所有聚集条形的最外层有一个完整外框，包裹整组图形

内容的提问来源于stack exchange，提问作者neuron