如何在管道运算符中使用Apply功能 [英] How to use apply function in a pipe operator

问题描述

我有一个数据框，其中有几个字符列，然后是几个数字列.我想使用％>％运算符添加一个新列，这是每行数字列中的最大值.

I have a dataframe which has a few character columns followed by a few numerical columns. I want to add a new column using the %>% operators which is the highest value from the numerical columns per row.

假设数据框如下所示:

字符1，字符2，值1，值2，值3

character1, character2, value1, value2, value3

字符串"，字符串"，5、7、4

"string", "string", 5, 7, 4

字符串"，字符串"，3、4、2

"string", "string", 3, 4, 2

字符串"，字符串"，2、8、6

"string", "string", 2, 8, 6

然后，新列的第一行应为7，第二行应为4，最后一行应为8.我正在尝试在管道运算符中使用apply函数，但无法正常工作.

Then the new column should be 7 for the first row, 4 for second row and 8 for last row. I am trying to use the apply function in the pipe operator but it's not working properly.

new_df <- old_df %>%
  mutate(new_column = apply(value1:value3, 1, max))

它返回错误:数值表达式只有首先使用的XXX值.

It returns error: Numerical expression has XXX values only first used.

我也尝试使用max(value1:value3)而不是apply，但这也不起作用.

I also tried using max(value1: value3) instead of apply but that doesn't work either.

推荐答案

您可以使用 dplyr 中的 rowwise :

library(dplyr)
df %>% 
  rowwise() %>% 
  mutate(new_column = max(c_across(value1:value2)))

# A tibble: 3 x 6
# Rowwise: 
  character1 character2 value1 value2 valu3 new_column
  <chr>      <chr>       <int>  <int> <int>      <int>
1 string     string          5      7     4          7
2 string     string          3      4     2          4
3 string     string          2      8     6          8

数据

library(tidyverse)
df <- tibble::tribble(
          ~character1,           ~character2, ~value1, ~value2, ~valu3,
  "string", "string", 5L, 7L, 4L,
  "string", "string", 3L, 4L, 2L,
  "string", "string", 2L, 8L, 6L
  )

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