旋转 dplyr 的 tibble 摘要的简单方法

Question

我正在寻找一种简单的方法来旋转dplyr 的tibble 摘要。

假设我正在做这样的事情，

# install.packages(c("dplyr"), dependencies = TRUE)
library(dplyr) 

mtcars %>% 
    group_by(am)  %>%
    summarise(
        n = n(),
        Mean_disp = mean(disp),
        Mean_hp = mean(hp),
        Mean_qsec = mean(qsec),
        Mean_drat = mean(drat)
             )
#>     # A tibble: 2 x 6
#>      am     n Mean_disp  Mean_hp Mean_qsec Mean_drat
#>   <dbl> <int>     <dbl>    <dbl>     <dbl>     <dbl>
#> 1     0    19  290.3789 160.2632  18.18316  3.286316
#> 2     1    13  143.5308 126.8462  17.36000  4.050000

但是，我想要的是或多或少像这样的输出，

#> # A tibble: 5 x 2
#>    am <dbl>             0           1
#>   n <int>              19          13
#>   Mean_disp <dbl>     290.3789    143.5308
#>   Mean_hp <dbl>       160.2631    126.8462
#>   Mean_qsec <dbl>      18.183158   17.36000
#>   Mean_drat <dbl>       3.286316    4.050000

我意识到我可以使用t()，但这会将小标题转换为列表并弄乱格式。

Answer 1

也许聚集然后再次传播：

library(dplyr) 
library(tidyr)

mtcars %>% 
  group_by(am)  %>%
  summarise(
    n = n(),
    Mean_disp = mean(disp),
    Mean_hp = mean(hp),
    Mean_qsec = mean(qsec),
    Mean_drat = mean(drat)) %>%
  gather(key = key, value = value, -am) %>% 
  spread(key = am, value = value)


# # A tibble: 5 x 3
#         key        `0`      `1`
# *     <chr>      <dbl>    <dbl>
# 1 Mean_disp 290.378947 143.5308
# 2 Mean_drat   3.286316   4.0500
# 3   Mean_hp 160.263158 126.8462
# 4 Mean_qsec  18.183158  17.3600
# 5         n  19.000000  13.0000

---

另一个选项，gather 在 group_by 之前，然后获取所有选定列的平均值，然后再次 spread（但不确定如何添加 @ 987654322@):

mtcars %>% 
  select(am, disp, hp, qsec, drat) %>% 
  gather(key = key, value = value, -am) %>% 
  group_by(am, key)  %>%
  summarise(myMean = mean(value)) %>%
  spread(key = am, value = myMean)

# # A tibble: 4 x 3
#     key        `0`      `1`
# * <chr>      <dbl>    <dbl>
# 1  disp 290.378947 143.5308
# 2  drat   3.286316   4.0500
# 3    hp 160.263158 126.8462
# 4  qsec  18.183158  17.3600

Answer 2

  new_tibble <- as.data.frame(t(mt_cars_df)) %>% 
  as_tibble()

  new_tibble$name <- names(mt_cars_df) %>%
    select(name, V1, V2)

根据this，在小标题中不推荐使用row.names，因此将它们作为键列添加是处理这种情况的合乎逻辑的方式。这留下了一个需要重新排序列的小标题。