r - 对数据集中的多个配对列使用ivot_longer

Question

我有一个看起来像这样的数据集:

input <- 
  data.frame(
    event = 1:2,
    url_1 = c("g1", "g3"),
    name_1 = c("dc", "nyc"),
    url_2 = c("g2", "g4"),
    name_2 = c("sf", "la"))

本质上，有一对以宽形式粘在一起的索引列。我想转换为long以给出以下输出:

output <- 
  data.frame(
    event = c(1,1,2,2),
    url = c("g1", "g2", "g3", "g4"),
    name = c("dc", "sf", "nyc", "la"))

我想使用 pivot_longer做到这一点。我已经试过了:

input %>% 
  pivot_longer(contains("_"))

如何获得识别列对的功能？

Answer 1

您想在.value参数中使用names_to:

input %>%
  pivot_longer(
    -event, 
    names_to = c(".value", "item"), 
    names_sep = "_"
  ) %>% 
  select(-item)

# A tibble: 4 x 3
  event url   name 
  <int> <fct> <fct>
1     1 g1    dc   
2     1 g2    sf   
3     2 g3    nyc  
4     2 g4    la   

从 this article on pivoting:

Note the special name .value: this tells pivot_longer() that that part of the column name specifies the “value” being measured (which will become a variable in the output).