如何移除ggplot2中geom_col列间黑线但保留分块轮廓？

我绘制了堆叠柱形图，希望移除geom_col中各堆叠部分之间的黑色分隔线，但保留wild、landrace这类分组块的整体轮廓。基于我当前的代码是否可以实现该需求？

对应的图表效果：

当前使用的示例代码：

library(ggplot2)
library(forcats)

ggplot(tbl2, aes(factor(sampleID), value, fill=comp)) +
  geom_col(color="black", size=0.1, width=1) +
  facet_grid(~fct_inorder(variety), switch="x", scales="free", space="free") +
  theme_minimal() + labs(x="Individuals", title="K=3", y="components") +
  scale_y_continuous(expand=c(0, 0)) +
  scale_x_discrete(expand=expand_scale(add=1)) +
  theme(
    panel.spacing.x=unit(0.1, "lines"),
    axis.text.x=element_blank(),
    panel.grid=element_blank()
  ) +
  scale_fill_brewer(palette="Paired", guide='none')

数据tbl2的结构：

structure(list(sampleID = c("INLUP00165", "INLUP00165", "INLUP00165", 
"INLUP00169", "INLUP00169", "INLUP00169", "INLUP00208", "INLUP00208", 
"INLUP00208", "INLUP00214", "INLUP00214", "INLUP00214", "INLUP00228", 
"INLUP00228", "INLUP00228", "INLUP00233", "INLUP00233", "INLUP00233", 
"INLUP00245", "INLUP00245", "INLUP00245", "INLUP00325", "INLUP00325", 
"INLUP00325", "INLUP00332", "INLUP00332", "INLUP00332", "INLUP00393", 
"INLUP00393", "INLUP00393", "INLUP00418", "INLUP00418", "INLUP00418", 
"INLUP00496", "INLUP00496", "INLUP00496"), variety = c("wild", 
"wild", "wild", "landrace", "landrace", "landrace", "wild", "wild", 
"wild", "wild", "wild", "wild", "landrace", "landrace", "landrace", 
"wild", "wild", "wild", "landrace", "landrace", "landrace", "landrace", 
"landrace", "landrace", "landrace", "landrace", "landrace", "landrace", 
"landrace", "landrace", "landrace", "landrace", "landrace", "landrace", 
"landrace", "landrace"), comp = c("comp1", "comp2", "comp3", 
"comp1", "comp2", "comp3", "comp1", "comp2", "comp3", "comp1", 
"comp2", "comp3", "comp1", "comp2", "comp3", "comp1", "comp2", 
"comp3", "comp1", "comp2", "comp3", "comp1", "comp2", "comp3", 
"comp1", "comp2", "comp3", "comp1", "comp2", "comp3", "comp1", 
"comp2", "comp3", "comp1", "comp2", "comp3"), value = c(0.000304534914903343, 
0.999695539474487, 5.66402567378596e-16, 7.25639850429616e-08, 
0.99999988079071, 7.41350128733039e-16, 2.27430740759918e-42, 
1, 1.40129846432482e-45, 0, 1, 1.26116861789234e-44, 1, 3.6168054052767e-30, 
6.73797980640088e-16, 7.37646416837379e-07, 0.999999284744263, 
1.86443519971077e-23, 1, 2.82813122498233e-29, 4.54367988546311e-14, 
6.76272702548886e-06, 1.06498683288686e-43, 0.999993205070496, 
0, 1, 0, 3.04290442727506e-05, 4.66462843997956e-16, 0.999969601631165, 
4.25612745047488e-09, 1, 5.97792615408821e-09, 1.18218178221686e-16, 
1, 3.16024730889457e-37)), class = "data.frame", row.names = c(NA, 
-36L))

可以实现，只需调整代码的两个核心部分：

1. 移除堆叠柱形内部的分隔线：去掉geom_col中的color="black"参数，让堆叠块之间无黑色线条。
2. 添加分组整体轮廓：通过geom_rect为每个variety分组绘制外框，需要先计算每个分组对应的x轴范围。

修改后的完整代码：

library(ggplot2)
library(forcats)
library(dplyr)

# 计算每个variety分组的x轴起始和结束位置
group_bounds <- tbl2 %>%
  distinct(sampleID, variety) %>%
  group_by(variety) %>%
  mutate(n = n(),
         x_start = 0.5,  # 离散x轴刻度以整数为中心，外框起始设为0.5
         x_end = n + 0.5) %>%  # 外框结束位置为样本数量+0.5
  distinct(variety, x_start, x_end)

ggplot(tbl2, aes(factor(sampleID), value, fill=comp)) +
  # 绘制堆叠柱形，移除内部分隔线
  geom_col(color=NA, width=1) +
  # 为每个分组添加黑色外框
  geom_rect(data=group_bounds,
            aes(xmin=x_start, xmax=x_end, ymin=0, ymax=1),
            inherit.aes=FALSE, color="black", size=0.1, fill=NA) +
  facet_grid(~fct_inorder(variety), switch="x", scales="free", space="free") +
  theme_minimal() + 
  labs(x="Individuals", title="K=3", y="components") +
  scale_y_continuous(expand=c(0, 0)) +
  scale_x_discrete(expand=expand_scale(add=1)) +
  theme(
    panel.spacing.x=unit(0.1, "lines"),
    axis.text.x=element_blank(),
    panel.grid=element_blank()
  ) +
  scale_fill_brewer(palette="Paired", guide='none')

关键说明 #

• geom_col(color=NA)：将堆叠柱形的边框设为透明，彻底移除内部堆叠块之间的黑色分隔线。
• geom_rect：基于提前计算的分组x轴范围，绘制仅带黑色边框的空心矩形，刚好包围整个分组的所有柱形，实现分组整体轮廓的效果。

这样就能达到你想要的效果：堆叠部分无内部分隔线，每个wild/landrace分组有完整的外框轮廓。

内容的提问来源于stack exchange，提问作者Matteo