对分组变量进行汇总和子集设置

这将有助于:

library(tidyverse)

set.seed(100)
test_df <- data.frame(var_name=c(rep(LETTERS[1:3],each=3),"C"),
                      group_name=c(1,1,0,0,1,0,1,1,1,1),
                      obs_1=rnorm(10),
                      obs_2=rnorm(10))

# function to calculate delta
delta_f = function(x) x[2]-x[1]

test_df %>%
  group_by(var_name, group_name) %>%                          # for each combination of var and group
  summarise_at(vars(matches("obs")), median) %>%              # get the median for all columns that match "obs"
  arrange(var_name, group_name) %>%                           # for each var get group == 0 in first row and group == 1 in second row
  summarise_at(vars(matches("obs")), funs(delta = delta_f))   # apply delta function

# # A tibble: 3 x 3
#   var_name obs_1_delta obs_2_delta
#   <fct>          <dbl>       <dbl>
# 1 A             -0.106       0.295
# 2 B             -0.486      -0.232
# 3 C             NA          NA 

看起来像 arrange() 部分是不必要的,因为分组会自动按所需方式排列行。但是,最好保持这种状态,以防将来由于包更新而导致行为改变。

为了计数你可以用这个

test_df %>%
  mutate(group_name = paste0("n_group", group_name)) %>%
  count(var_name, group_name) %>%
  spread(group_name, n, fill = 0)

# # A tibble: 3 x 3
#   var_name n_group0 n_group1
#   <fct>       <dbl>    <dbl>
# 1 A               1        2
# 2 B               2        1
# 3 C               0        4

然后把两张桌子连在一起 var_name .