将列名附加到由下划线分隔的值的开头答案

【问题标题】：Append column name to the beginning of values separated by an underscore将列名附加到由下划线分隔的值的开头
【发布时间】：2021-02-07 20:20:21
【问题描述】：

如何将列名附加到列中每个值的开头，用“_”分隔，跳过第一列（或者，等效地，选择第二列和第三列）？

multiple=data.frame(id=c(1:6), 
     status=c("good", "bad", "ok", "ok", "good", "bad"), 
     breakfast=c("eggs", "sausage", "eggs", "sausage", "sausage", "eggs"))
# Desired:
#id status breakfast
#1  status_good breakfast_eggs
#2  status_bad  breakfast_sausage
#3  status_ok   breakfast_eggs
#4  status_ok   breakfast_sausage
#5  status_good breakfast_sausage
#6  status_bad  breakfast_eggs

【问题讨论】：

标签： r dataframe dplyr stringr

【解决方案1】：

这是一个带有tidyverse 的选项，我们循环across 列并粘贴相应的列名（cur_column()）

library(dplyr)
library(stringr)
multiple %>%
    mutate(across(c(status, breakfast), ~ str_c(cur_column(), "_", .)))

-输出

#  id      status         breakfast
#1  1 status_good    breakfast_eggs
#2  2  status_bad breakfast_sausage
#3  3   status_ok    breakfast_eggs
#4  4   status_ok breakfast_sausage
#5  5 status_good breakfast_sausage
#6  6  status_bad    breakfast_eggs

【讨论】：

【解决方案2】：

在base R中，我们可以使用Map：

multiple[-1] <- Map(function(x, y) paste(x, y, sep = '_'), 
                     names(multiple)[-1], multiple[-1])

或者用purrr的imap_dfc：

multiple[-1] <- purrr::imap_dfc(multiple[-1], ~paste(.y, .x, sep = '_'))
multiple

#  id      status         breakfast
#1  1 status_good    breakfast_eggs
#2  2  status_bad breakfast_sausage
#3  3   status_ok    breakfast_eggs
#4  4   status_ok breakfast_sausage
#5  5 status_good breakfast_sausage
#6  6  status_bad    breakfast_eggs

【讨论】：