R dplyr mutate_at 访问 colnames

如何访问正在处理的列名dplyr::mutate_at?

假设我们想要将数据框的列转换为因子，其级别存储在单独的列表中。

df <- data.frame("C1"=c("A","B","C"), "C2"=c("D","E","F"))
df
  C1 C2
1  A  D
2  B  E
3  C  F

lst <- list("C2"=c("F","E","D"), "C3"=c("G","H","I"))
lst
$C2
[1] "F" "E" "D"

$C3
[1] "G" "H" "I"

以下所有情况都会触发错误或将所有列值替换为 NA：

df %>%
mutate_at(vars(C2), function(x) factor(x, levels=lst$.))

df %>%
mutate_at(vars(C2), function(x) factor(x, levels=lst[[colnames(.)]]))

df %>%
mutate_at(vars(C2), function(x){col = as.name(.); factor(x, levels=lst$col))

您可以使用Map在基础 R 或map2 from purrr使用获取公共列后intersect.

cols <- intersect(names(lst), names(df))
df[cols] <- Map(function(x, y) factor(x, levels = y), df[cols], lst[cols])

Or

df[cols] <- purrr::map2(df[cols], lst[cols], ~factor(.x, levels = .y))