mutate_at与mutate_if的结合

Question

我正在我的包中创建一个通用函数。目标是查找列百分比，如果它们是parse_number列，则在它们上使用character。我还没有找到使用mutate_at和ifelse的解决方案。我在下面贴了一张复述纸。

 library(tidyverse)


df <- tibble::tribble(
  ~name, ~pass_percent, ~attendance_percent, ~grade,
  "Jon",         "90%",                0.85,    "B",
  "Jim",        "100%",                   1,    "A"
  )

percent_names <- df %>% select(ends_with("percent"))%>% names()


# Error due to attendance_percent already being in numeric value

if (percent_names %>% length() > 0) {
    df <-
      df %>%
      dplyr::mutate_at(percent_names, readr::parse_number)
  }
#> Error in parse_vector(x, col_number(), na = na, locale = locale, trim_ws = trim_ws): is.character(x) is not TRUE

Answer 1

您的attendance_percent变量是数字变量，而不是字符，而parse_number只需要字符变量，请参见这里。因此，解决办法是：

edited_parse_number <- function(x, ...) {
  if (mode(x) == 'numeric') {
    x
  } else {
    parse_number(x, ...)
  }
}


df %>%
  dplyr::mutate_at(vars(percent_names), edited_parse_number)

#  name  pass_percent attendance_percent grade
#  <chr>        <dbl>              <dbl> <chr>
#1 Jon             90               0.85 B    
#2 Jim            100               1    A   

或

如果不想使用该额外函数，请在开始时提取字符变量：

percent_names <- df %>% 
  select(ends_with("percent")) %>% 
  select_if(is.character) %>% 
  names()
percent_names
# [1] "pass_percent"


df %>%
  dplyr::mutate_at(vars(percent_names), parse_number)
#   name  pass_percent attendance_percent grade
#   <chr>        <dbl>              <dbl> <chr>
# 1 Jon             90               0.85 B    
# 2 Jim            100               1    A    

Answer 2

或者，无需创建函数，只需将ifelse语句添加到mutate_at中，如：

if (percent_names %>% length() > 0) {
  df <-
    df %>% rowwise() %>%
    dplyr::mutate_at(vars(percent_names), ~ifelse(is.character(.), 
                                                  parse_number(.),
                                                  .))
}

Source: local data frame [2 x 4]
Groups: <by row>

# A tibble: 2 x 4
  name  pass_percent attendance_percent grade
  <chr>        <dbl>              <dbl> <chr>
1 Jon             90               0.85 B    
2 Jim            100               1    A