如何用ggplot创建分组堆叠柱状图（非分面形式）

需要用ggplot绘制堆叠柱状图，具体需求：

• X轴显示月份编号
• Y轴为各物种每月的总数量
• 同一月份下，有多少年份的采样数据就并列展示多少根堆叠柱（不同年份的柱子对应同一月份）
  现有代码通过分面展示年份，不符合预期效果。

示例数据集 #

Sp <- data.frame(Species = c("A","A","A","A","A","A","A","A","A","A","A","B","B","B","B","B","C","C","C","C","C","C","C","C","C","C","C","C","C","C","C","C","C","C","C","C","C","C"),
Month= c("2","3","4","4","4","7","3","4","4","5","6","4","5","6","6","7","4","3","4","5","6","7","3","4","4","5","6","4","5","6","4","5","6","2","2","8","5","5"),
Year= c("2018","2005","2006","2006","2006","2006","2008","2008","2008","2008","2018","2009","2009","2009","2018","2009","2009","2009","2009","2009","2018","2005","2005","2005","2006","2006","2005","2006","2005","2005","2005","2009","2009","2009","2018","2018","2018","2018"))

现有代码 #

Sp%>% group_by(Month, Year, Species)%>%
 ggplot(aes(Month)) +  
  geom_bar(aes(fill= Species),stat='count')+
  facet_wrap( ~ Year, nrow = 1)

输出差异 #

• 当前输出：按年份分面，每个年份单独展示该年份的月份堆叠柱
• 预期效果：X轴为月份，同一月份下并列展示对应年份的堆叠柱，柱子内部按物种堆叠，体现各物种当月总数量

1. 数据预处理 #

先按月份、年份、物种分组统计数量，同时将月份转为有序因子，保证X轴按数字顺序排列：

library(dplyr)
library(ggplot2)

# 统计各分组的个体数量，并整理月份顺序
Sp_sum <- Sp %>%
  group_by(Month, Year, Species) %>%
  summarise(Count = n(), .groups = "drop") %>%
  mutate(Month = factor(Month, levels = sort(unique(Month))))

2. 绘制目标堆叠柱状图 #

将Year作为并列分组的依据，使用position_dodge实现同一月份下不同年份柱子的并列展示：

ggplot(Sp_sum, aes(x = Month, y = Count, fill = Species, group = Year)) +
  geom_col(position = position_dodge(preserve = "single")) +
  labs(x = "月份", y = "物种总数量", fill = "物种") +
  theme_bw()

关键说明 #

• geom_col：直接使用预处理好的Count值，比geom_bar(stat='count')更清晰可控
• position_dodge(preserve = "single")：确保同一月份下的不同年份柱子并列，且即使某月份只有一个年份数据，柱子宽度也与其他月份一致，避免视觉上的宽窄不一
• 有序因子Month：避免X轴按字母顺序排列（比如"10"排在"2"前面），保证月份按数字从小到大展示

内容的提问来源于stack exchange，提问作者RGR_288