dplyr使用可变列进行突变 [英] dplyr mutate using variable columns

问题描述

我正在尝试使用mutate创建一个具有基于特定列的值的新列.

I am trying to use mutate to create a new column with values based on a specific column.

示例最终数据帧(我正在尝试创建new_col):

Example final data frame (I am trying to create new_col):

x = tibble(colA = c(11, 12, 13),
           colB = c(91, 92, 93),
           col_to_use = c("colA", "colA", "colB"),
           new_col = c(11, 12, 93))

我想做类似的事情:

x %>% mutate(new_col = col_to_use)

除了列内容以外，我想将它们转换为变量.我开始:

Except instead of column contents, I would like to transform them to a variable. I started with:

col_name = "colA"
x %>% mutate(new_col = !!as.name(col_name))

与静态变量一起使用.但是，我一直无法更改代表列的变量.如何根据其他列的内容获取列名?

That works with a static variable. However, I have been unable to change the variable to represent the column. How do I take a column name based on contents of a different column?

这个问题基本上是相反的: dplyr-mutate:使用动态变量名.我无法使解决方案适应我的问题.

This question is basically the opposite of this: dplyr - mutate: use dynamic variable names. I wasn't able to adapt the solution to my problem.

推荐答案

我们可以使用 purrr 包即可完成此任务.

We can use imap_dbl and pluck from the purrr package to achieve this task.

library(tidyverse)

x <- tibble(colA = c(11, 12, 13),
           colB = c(91, 92, 93),
           col_to_use = c("colA", "colA", "colB"))

x2 <- x %>%
  mutate(new_col = imap_dbl(col_to_use, ~pluck(x, .x, .y)))

x2
# # A tibble: 3 x 4
#   colA  colB col_to_use new_col
#  <dbl> <dbl> <chr>        <dbl>
# 1   11.   91. colA           11.
# 2   12.   92. colA           12.
# 3   13.   93. colB           93.

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