将 NA 值替换为 dplyr 中因子变量的模态值

Question

假设我有以下数据框。我想用最常出现的响应 a

替换 NA

df <- read.table(text = "id result
1 a
2 a
3 a
4 b
5 NA", header = T)

我正在寻找这样的东西:

calculate_mode <- function(x) {
  uniqx <- unique(x)
  uniqx[which.max(tabulate(match(x, uniqx)))]
}

df = df %>% 
  mutate(result = ifelse(is.na(result), calculate_mode(result), result))

但我不确定在定义自定义函数之外是否有更“整洁”的方法来执行此操作。

Answer 1

  library(dplyr)
  library(tidyr)
  
  # manually get the most frequent values and tidyr::replace_na 
  most_value <- table(df$result) %>% sort(decreasing = TRUE) %>%
    head(1) %>% names()
  df %>% replace_na(list(result = most_value))
#>   id result
#> 1  1      a
#> 2  2      a
#> 3  3      a
#> 4  4      b
#> 5  5      a

动态应用于多列

  # do it acorss multiple column - still kind of using functions
  most <- function(x) {
    table(x) %>% sort(decreasing = TRUE) %>% head(1) %>% names()
  }
  multiple_column <- left_join(df, df, by = "id")
  multiple_column
#>   id result.x result.y
#> 1  1        a        a
#> 2  2        a        a
#> 3  3        a        a
#> 4  4        b        b
#> 5  5     <NA>     <NA>
  
  multiple_column %>%
    mutate(across(.cols = starts_with("result"), .fns = function(x) {
      if_else(is.na(x), most(x), x)
    }))
#>   id result.x result.y
#> 1  1        a        a
#> 2  2        a        a
#> 3  3        a        a
#> 4  4        b        b
#> 5  5        a        a

^{由 reprex package 于 2021 年 4 月 24 日创建(v2.0.0)}