修复ggplot2堆叠柱状图setup_params()函数y轴映射错误

问题背景 #

使用如下结构的数据框绘制堆叠柱状图：

df = structure(list(Year_Publication = c(1989L, 1994L, 2001L, 2002L, 
                                         2002L, 2004L, 2006L, 2007L, 2009L, 2011L, 2012L, 2013L, 2014L, 
                                         2015L, 2016L, 2017L, 2017L, 2017L, 2018L, 2018L, 2018L, 2019L, 
                                         2019L, 2019L, 2020L, 2020L, 2020L, 2020L, 2021L, 2021L, 2022L, 
                                         2022L, 2022L, 2022L), Taxa = c("Cervidae", "Teleostei", "Chondrichtyes", 
                                                                        "Chondrichtyes", "Gastropoda", "Teleostei", "Malacostraca", "Teleostei", 
                                                                        "Teleostei", "Teleostei", "Teleostei", "Teleostei", "Teleostei", 
                                                                        "Teleostei", "Teleostei", "Chondrichtyes", "Teleostei", "Chondrostei", 
                                                                        "Teleostei", "Chondrichtyes", "Decapoda", "Teleostei", "Gastropoda", 
                                                                        "Chondrichtyes", "Chondrostei", "Teleostei", "Bivalvia", "Tetrapoda", 
                                                                        "Teleostei", "Orthoptera", "Chondrichtyes", "Teleostei", "Reptilia", 
                                                                        "Bovidae"), Total_Species_Per_Taxa = c(1L, 2L, 1L, 1L, 3L, 1L, 
                                                                                                               1L, 1L, 2L, 4L, 2L, 1L, 1L, 2L, 4L, 2L, 4L, 1L, 7L, 3L, 1L, 6L, 
                                                                                                               1L, 3L, 1L, 7L, 2L, 1L, 1L, 1L, 4L, 4L, 1L, 1L), Total_Species_Per_Pub = c(1L, 
                                                                                                                                                                                          2L, 1L, 4L, 4L, 1L, 1L, 1L, 2L, 4L, 2L, 1L, 1L, 2L, 4L, 7L, 7L, 
                                                                                                                                                                                          7L, 11L, 11L, 11L, 10L, 10L, 10L, 11L, 11L, 11L, 11L, 2L, 2L, 
                                                                                                                                                                                          10L, 10L, 10L, 10L)), class = "data.frame", row.names = c(NA, 
                                                                                                                                                                                                                                                    -34L))

尝试以下两段代码时触发错误：

ggplot(data = taxa_diversity, aes(x = `Year_Publication`, fill = Taxa)) +
  geom_bar(aes(y = `Total_Species_Per_Pub`), stat = "count")

ggplot(data = taxa_diversity, aes(x = `Year_Publication`, y = `Total_Species_Per_Pub`, fill = Taxa)) +
  geom_bar(stat = "count")

错误信息：

Error in `geom_bar()`:
! Problem while computing stat.
ℹ Error occurred in the 1st layer.
Caused by error in `setup_params()`:
! `stat_count()` must only have an x or y aesthetic.
Run `rlang::last_error()` to see where the error occurred.

移除y轴设置后图表可生成，但y轴数值不符合预期。

解决方案 #

1. 报错原因 #

stat="count"的作用是统计x/y轴每个分组的行数，它不需要手动指定y轴数值。当你同时指定y轴和stat="count"时，ggplot会因为逻辑冲突抛出错误。移除y轴后，它默认统计每年每个Taxa的行数，这和你需要的物种数量数值不符，所以y轴显示错误。

2. 正确代码 #

你的数据已经是汇总好的（每个Year_Publication+Taxa对应的物种数Total_Species_Per_Taxa，且同一年份的该数值之和等于Total_Species_Per_Pub），因此需要使用stat="identity"，告诉ggplot直接使用y轴指定的数值绘制柱子：

ggplot(data = df, aes(x = Year_Publication, y = Total_Species_Per_Taxa, fill = Taxa)) +
  geom_bar(stat = "identity")

3. 补充说明 #

• 这段代码会生成堆叠柱状图，每个年份柱子的总高度等于该年份的Total_Species_Per_Pub，每个分段对应不同Taxa的Total_Species_Per_Taxa，符合你的数据逻辑。
• 如果需要调整图表样式（比如添加标签、修改颜色、调整坐标轴），可以在代码后继续添加labs()、scale_fill_manual()等图层。

内容的提问来源于stack exchange，提问作者Kristen Cyr