dplyr多级分组求和报错问题求助

问题描述 #

我在处理鸟类调查数据的分组求和时遇到问题：数据包含多个样地（site）、调查点（point），每年开展1-2次调查（visit）统计鸟类物种（species）数量（abundance），但因距离区间划分，同一物种在单次调查中会有多条记录。为估算物种丰富度，需要对单次调查的同一物种数量求和。

我用dplyr编写的代码：

bird.group <- group_by(bird.use, site, point, year, visit, species, sum.abund=sum(abundance))

运行后报错：

Error in group_by():
! Problem adding computed columns.
Caused by error in mutate():
! Problem while computing sum.abund = sum(abundance).
Caused by error in sum():
! invalid 'type' (character) of argument
Run rlang::last_error() to see where the error occurred.

附示例数据：

structure(list(site = c("BethWater", "BethWater", "BethWater", "BethWater", "BethWater", "BethWater", "BethWater", "BethWater", "BethWater", "BethWater", "BethWater", "BethWater", "BethWater", "BethWater", "BethWater", "BethWater", "BethWater", "BethWater", 
"BethWater", "BethWater", "BethWater", "BethWater", "BethWater", "BethWater", "BethWater"), point = c("1", "1", "1", "1", "1", "1", "1", "1", "1", "1", "1", "1", "1", "1", "1", "1", "1", "1", 
"2", "2", "2", "2", "2", "2", "2"), year = c(2020L, 2020L, 2020L, 2020L, 2020L, 2020L, 2020L, 2020L, 2020L, 2020L, 2020L, 2020L, 2020L, 2020L, 2020L, 2020L, 2020L, 2020L, 2020L, 2020L, 2020L, 
2020L, 2020L, 2020L, 2020L), visit = c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L), species = c("BAWW", "CSWA", "CSWA", "COYE", "EATO", 
"EATO", "EATO", "FISP", "GRCA", "GRCA", "MODO", "OVEN", "REVI", "REVI", "PRAW", "AMRE", "ALFL", "YBCU", "BAWW", "BAWW", "CSWA", "COYE", "COYE", "EATO", "EATO"), abundance = c("2", "1", "1", 
"1", "1", "2", "1", "1", "1", "2", "1", "1", "1", "2", "1", "2", "1", "1", "1", "1", "1", "1", "1", "2", "2")), row.names = c(NA, 25L), class = "data.frame")

问题分析与修正 #

1. 核心错误原因 #

• group_by()仅用于指定分组字段，不能直接在函数内执行求和计算，求和需配合summarise()或mutate()完成
• 示例数据中abundance列是字符类型（值带引号），sum()函数无法对字符类型进行运算，需先转换为数值型

2. 修正后的代码 #

library(dplyr)

# 第一步：将字符型的abundance转为数值型
bird.use <- bird.use %>%
  mutate(abundance = as.numeric(abundance))

# 第二步：分组并计算每个组的总数量
bird.group <- bird.use %>%
  group_by(site, point, year, visit, species) %>%
  summarise(sum.abund = sum(abundance), .groups = "drop")

代码说明 #

• mutate(abundance = as.numeric(abundance))：转换数据类型，确保求和函数能正常工作
• group_by(...)：仅定义分组维度，不包含计算逻辑
• summarise(sum.abund = sum(abundance), .groups = "drop")：对每个分组执行求和，.groups = "drop"参数用于取消分组状态，返回普通数据框（若需保留分组可省略该参数）

内容的提问来源于stack exchange，提问作者Jeff Stratford