R语言：如何通过列号而非列名在formattable中指定格式化列？

你的核心需求是通过列号而非列名给formattable表格设置格式化规则，避免每年因列名变化修改代码。之前的代码失败原因是直接将列数据对象作为格式化规则的键，而formattable需要的是列名或位置定位的规则。以下是两种可行的解决方法：

方法一：通过列号获取列名，动态指定格式化规则 #

利用列号提取对应列名，再通过tidyeval语法将列名作为格式化规则的键，实现动态绑定：

library(formattable)

# 构建示例数据框
bach_STEM_wide <- data.frame(
  Name = c("Technology", "Science", "Engineering"),
  "Pct. Diff. from 2013 to 2023" = c(-5.2, 7.3, -1.8),
  "Pct. Diff. from 2022 to 2023" = c(2.1, -3.5, 1.2))

# 指定目标列的列号
target_col_num <- 2
second_col_num <- 3

# 从列号提取对应列名
target_col_name <- colnames(bach_STEM_wide)[target_col_num]
second_col_name <- colnames(bach_STEM_wide)[second_col_num]

# 生成formattable表格
formattable(bach_STEM_wide, align = "l", list(
  Name = formatter(
    "span",
    style = x ~ ifelse(x == "Technology", 
                       style(font.weight = "bold"), NA)),
  # 使用!!和:=将列名变量作为规则的键
  !!target_col_name := formatter(
    "span",
    style = x ~ style(color = ifelse(x < 0 , "orange", "blue")),
    x ~ icontext(ifelse(x < 0, "arrow-down", "arrow-up"), x)),
  !!second_col_name := formatter(
    "span",
    style = x ~ style(color = ifelse(x < 0 , "orange", "blue")),
    x ~ icontext(ifelse(x < 0, "arrow-down", "arrow-up"), x))
))

方法二：直接用area()通过列号定位列（更推荐） #

formattable支持area(col = 列号)语法直接定位目标列，无需处理列名，完全依赖位置设置规则，最适合年度列名变化的场景：

library(formattable)

# 构建示例数据框
bach_STEM_wide <- data.frame(
  Name = c("Technology", "Science", "Engineering"),
  "Pct. Diff. from 2013 to 2023" = c(-5.2, 7.3, -1.8),
  "Pct. Diff. from 2022 to 2023" = c(2.1, -3.5, 1.2))

# 生成formattable表格
formattable(bach_STEM_wide, align = "l", list(
  Name = formatter(
    "span",
    style = x ~ ifelse(x == "Technology", 
                       style(font.weight = "bold"), NA)),
  # 直接用列号指定目标列
  area(col = 2) ~ formatter(
    "span",
    style = x ~ style(color = ifelse(x < 0 , "orange", "blue")),
    x ~ icontext(ifelse(x < 0, "arrow-down", "arrow-up"), x)),
  area(col = 3) ~ formatter(
    "span",
    style = x ~ style(color = ifelse(x < 0 , "orange", "blue")),
    x ~ icontext(ifelse(x < 0, "arrow-down", "arrow-up"), x))
))

如果需要批量处理所有数值列（比如从第2列到最后一列），可以简化为：

area(col = 2:ncol(bach_STEM_wide)) ~ formatter(
  "span",
  style = x ~ style(color = ifelse(x < 0 , "orange", "blue")),
  x ~ icontext(ifelse(x < 0, "arrow-down", "arrow-up"), x))

内容的提问来源于stack exchange，提问作者tangerine7199