r - 如何在我的数据框中进行大量的 t.test(多组/结果，多定量变量)？

Question

通过在 R 中运行多个 t.test(根据多个定量变量比较多个组)，我想在 R 中得到这样的结果:

我尝试并修改了此处提供的解决方案: dplyr summarise multiple columns using t.test

library(dplyr)
library(tidyr)
data(mtcars)


vars_to_test <- c("disp","hp","drat","wt","qsec")
iv <- c("vs", "am")


mtcars %>%
  summarise_each_(
    funs_( 
      sprintf("stats::t.test(.[%s == 0], .[%s == 1])$p.value",iv,iv)
    ), 
    vars = vars_to_test)

这是输出:

     disp_$..1      hp_$..1  drat_$..1      wt_$..1    qsec_$..1    disp_$..2   hp_$..2    drat_$..2     wt_$..2 qsec_$..2
1 2.476526e-06 1.819806e-06 0.01285342 0.0007281397 3.522404e-06 0.0002300413 0.2209796 5.266742e-06 6.27202e-06 0.2093498

我面临多个问题:

• (1) 我有两个警告消息，我不知道两个如何解决

Please use summarise_if(), summarise_at(), or summarise_all() instead: 

  - To map `funs` over all variables, use summarise_all()
  - To map `funs` over a selection of variables, use summarise_at()
This warning is displayed once per session. 
2: funs_() is deprecated. 
Please use list() instead

• (2) 如何让每个组/结果占一行？
• (3) 如何通过组名称更改“1”(第二行的第一个字符)(即:本例中的“vs”和“am”)？
• (4) 如何将此输出导出为数据框(如我开始的示例所示)

非常感谢您的帮助!

Answer 1

library(tidyverse)

vars_to_test <- c("disp","hp","drat","wt","qsec")
iv <- c("vs", "am")

expand.grid(vars_to_test, iv, stringsAsFactors = F) %>%              # create pairs of variables
  rowwise() %>%                                                      # for each pair
  mutate(p_val = t.test(mtcars[,Var1] ~ mtcars[,Var2])$p.value) %>%  # get p value from t.test
  spread(Var1, p_val)                                                # reshape output

# # A tibble: 2 x 6
#   Var2        disp       drat         hp       qsec         wt
#   <chr>      <dbl>      <dbl>      <dbl>      <dbl>      <dbl>
# 1 am    0.000230   0.00000527 0.221      0.209      0.00000627
# 2 vs    0.00000248 0.0129     0.00000182 0.00000352 0.000728