r - tidyr 聚集 : simultaneously gather and rename key?

Question

假设我有以下数据框:

> a <- data_frame(my_type_1_num_widgets = c(1, 2, 3), my_type_2_num_widgets = c(4, 5, 6))
> a
Source: local data frame [3 x 2]

  my_type_1_num_widgets my_type_2_num_widgets
1                     1                     4
2                     2                     5
3                     3                     6

我想做两件事:

1. 收集“num_widgets”列。
2. 重命名生成的键以删除“num_widgets”后缀。

我目前这样做的方式，以及我得到的正确/期望的输出:

> a %>% 
    rename(my_type_1 = my_type_1_num_widgets, 
           my_type_2 = my_type_2_num_widgets) %>% 
    gather(type, num_widgets, my_type_1:my_type_2)
Source: local data frame [6 x 2]

       type num_widgets
1 my_type_1           1
2 my_type_1           2
3 my_type_1           3
4 my_type_2           4
5 my_type_2           5
6 my_type_2           6

有没有一种方法可以一步完成？

Answer 1

尝试:

a %>% 
  gather(type, num_widgets) %>% ## gather the "num_widgets" columns
  mutate(type = sub("_num_widgets", "", type)) ## remove the suffix

给出:

#Source: local data frame [6 x 2]
#
#       type num_widgets
#1 my_type_1           1
#2 my_type_1           2
#3 my_type_1           3
#4 my_type_2           4
#5 my_type_2           5
#6 my_type_2           6