我有一个数据集，看起来像这样：

working_df %>% 
  select(user_type, ride_length, day_of_week) %>%
  as.tibble() %>% 
  print(n = 3)
    # A tibble: 4,324,766 × 3
      user_type ride_length day_of_week
      <chr>           <dbl> <ord>      
    1 Casual          34355 Saturday   
    2 Member          32035 Monday     
    3 Casual          29271 Saturday

我想创建一个表，提供每组用户每天的平均骑行长度。我使用SQL的CASE WHEN将一周中的天数划分为单独的列。请参见下面：

SELECT 
    COALESCE(user_type,'combined') AS user_type,
    AVG(CASE WHEN DAYNAME(started_at) = 'Monday' THEN TIMESTAMPDIFF(MINUTE,started_at, ended_at) ELSE NULL END) AS avg_ride_length_monday,
    AVG(CASE WHEN DAYNAME(started_at) = 'Tuesday' THEN TIMESTAMPDIFF(MINUTE,started_at, ended_at) ELSE NULL END) AS avg_ride_length_tuesday,
    AVG(CASE WHEN DAYNAME(started_at) = 'Wednesday' THEN TIMESTAMPDIFF(MINUTE,started_at, ended_at) ELSE NULL END) AS avg_ride_length_wednesday,
    AVG(CASE WHEN DAYNAME(started_at) = 'Thursday' THEN TIMESTAMPDIFF(MINUTE,started_at, ended_at) ELSE NULL END) AS avg_ride_length_thursday,
    AVG(CASE WHEN DAYNAME(started_at) = 'Friday' THEN TIMESTAMPDIFF(MINUTE,started_at, ended_at) ELSE NULL END) AS avg_ride_length_friday,
    AVG(CASE WHEN DAYNAME(started_at) = 'Saturday' THEN TIMESTAMPDIFF(MINUTE,started_at, ended_at) ELSE NULL END) AS avg_ride_length_saturday,
    AVG(CASE WHEN DAYNAME(started_at) = 'Sunday' THEN TIMESTAMPDIFF(MINUTE,started_at, ended_at) ELSE NULL END) AS avg_ride_length_sunday,
    AVG(TIMESTAMPDIFF(MINUTE,started_at, ended_at)) AS grand_total
FROM 
    bikes.work
GROUP BY 
    user_type WITH ROLLUP;

在我的研究中，我发现了dplyr：：case_when（），但我只看到过在一列中计算值的例子，我希望一周中的每一天都能展开。R是否有能力将结果推送到几列中？
编辑：感谢您的建议，我找到了这个潜在的答案：

working_df %>%
  mutate_at(vars(c(user_type, day_of_week)), funs(as.character(.))) %>% 
  bind_rows(mutate(., user_type = "Combined")) %>% 
  bind_rows(mutate(., day_of_week = "Grand_Total")) %>% 
  group_by(user_type, day_of_week) %>% 
  summarize(avg_ride_length_min = mean(ride_length))  %>% 
  pivot_wider(names_from = day_of_week,
              values_from = avg_ride_length_min,
              names_prefix = "avg_ride_length_")

 user_type avg_ride_length_Friday avg_ride_length_Grand_Total avg_ride_length_Monday avg_ride_length_Saturday avg_ride_length_Sunday
  <chr>                      <dbl>                       <dbl>                  <dbl>                    <dbl>                  <dbl>
1 Casual                      22.6                        24.2                   25.0                     27.0                   27.5
2 Combined                    16.5                        17.3                   16.8                     20.9                   20.8
3 Member                      12.4                        12.6                   12.2                     14.2                   14.0
  avg_ride_length_Thursday avg_ride_length_Tuesday avg_ride_length_Wednesday
                     <dbl>                   <dbl>                     <dbl>
1                     21.6                    21.6                      20.9
2                     15.5                    15.1                      14.9
3                     12.2                    11.9                      12.0