使用正则表达式匹配编辑（重新编码、折叠、排序）因子水平

Question

我发现在 R 中操作因子变量过于复杂。清洁因素时我经常想做的事情包括：

Resorting levels – 不仅仅是为了设置一个参考类别，而且还把所有级别按照逻辑（non-alphabetical顺序）汇总表。 x <- factor(x, levels = new.order)
重新编码/重命名因子级别 - 以简化名称 and/or 将多个类别合并为一组。对于 one-to-one 重新编码 levels(x) <- new.levels(x) 或 plyr::revalue，请参阅 here or here 示例。 car::recode 可以在单个语句中执行多个 one-to-many 匹配，但不支持正则表达式匹配。
删除关卡——不只是删除未使用的关卡，而是将一些关卡设置为缺失。（例如，那些有错误代码的）。 x <- factor(as.character(x), exclude = drop.levels)
添加级别 – 显示计数为零的类别。

如果有一个函数可以同时完成上述所有操作，允许模糊（正则表达式）匹配重新编码和删除因子，可以在其他函数中使用（例如 lapply 或 dplyr::mutate)，并具有简单（一致）的语法。

我已经在下面发布了我对此的最佳尝试作为答案，但是如果我遗漏了一个已经存在的函数或者代码是否可以改进，请告诉我。

编辑

我已经知道 forcats 包，它的副标题是 用于处理分类变量（因子）的工具 。该软件包有许多选项用于重新排序级别（'fct_infreq'、'fct_reorder'、'fct_relevel'、...）、recoding/grouping 级别（'fct_recode'、'fct_lump' , 'fct_collapse'), 降低等级 ('fct_recode'), 和增加等级 ('fct_expand').但是目前还没有支持正则匹配的计划(https://github.com/tidyverse/forcats/issues/214).

Answer 1

编辑：几年后，我在 github 上添加了 xfactor 函数来完成上述操作。它仍在进行中，所以如果有任何错误等，请告诉我。

devtools::install_github("jwilliman/xfactor")


library(xfactor)

# Create example factor
x <- xfactor(c("dogfish", "rabbit","catfish", "mouse", "dirt"))
levels(x)
#> [1] "catfish" "dirt"    "dogfish" "mouse"   "rabbit"

# Factor levels can be reordered by passing an unnamed vector to the levels
# statement. Levels not included in the replace statement get moved to the end
# or dropped if exclude = TRUE.
xfactor(x, levels = c("mouse", "rabbit"))
#> [1] dogfish rabbit  catfish mouse   dirt   
#> Levels: mouse rabbit catfish dirt dogfish

xfactor(x, levels = c("mouse", "rabbit"), exclude = TRUE)
#> [1] <NA>   rabbit <NA>   mouse  <NA>  
#> Levels: mouse rabbit

# Factor levels can be recoded, collapse, and ordered by passing a named
# vector to the levels statement. Where the vector names are the new factor
# levels and the vector values are regex expressions for the old levels.
# Duplicated new levels will be collapsed.

xfactor(x, levels = c("Sea" = "fish", "Land" = "rab|mou"))
#> [1] Sea  Land Sea  Land dirt
#> Levels: Sea Land dirt

# Factor levels can be dropped by passing a regex expression (or vector) to
# the exclude statement

xfactor(x, exclude = "fish")
#> [1] <NA>   rabbit <NA>   mouse  dirt  
#> Levels: dirt mouse rabbit

# The function will work within other functions

library(dplyr)
#> 
#> Attaching package: 'dplyr'
#> The following objects are masked from 'package:stats':
#> 
#>     filter, lag
#> The following objects are masked from 'package:base':
#> 
#>     intersect, setdiff, setequal, union
df <- data.frame(n = 1:5, x)
df %>%
  mutate(y = xfactor(x, levels = c("Sea" = "fish", "Land" = "rab|mou", "Air"), exclude = "di"))
#>   n       x    y
#> 1 1 dogfish  Sea
#> 2 2  rabbit Land
#> 3 3 catfish  Sea
#> 4 4   mouse Land
#> 5 5    dirt <NA>

^{由 reprex package (v0.3.0)}

于 2020-04-16 创建

使用正则表达式匹配编辑（重新编码、折叠、排序）因子水平

Edit (recode, collapse, order) factor levels with regex matching

r

regex

r-factor