str使用cat，因此无法将其转换为漂亮data.frame进行打印，但是可以模仿其功能创建一个data.frame，然后将其传递给您喜欢的rmarkdown表格式化程序（kable、pander等）：

library(knitr)
library(magrittr)
data.frame(variable = names(mtcars),
           classe = sapply(mtcars, typeof),
           first_values = sapply(mtcars, function(x) paste0(head(x),  collapse = ", ")),
           row.names = NULL) %>% 
  kable()

|variable |classe  |first_values                             |
|:--------|:-------|:----------------------------------------|
|mpg      |numeric |21, 21, 22.8, 21.4, 18.7, 18.1           |
|cyl      |numeric |6, 6, 4, 6, 8, 6                         |
|disp     |numeric |160, 160, 108, 258, 360, 225             |
|hp       |numeric |110, 110, 93, 110, 175, 105              |
|drat     |numeric |3.9, 3.9, 3.85, 3.08, 3.15, 2.76         |
|wt       |numeric |2.62, 2.875, 2.32, 3.215, 3.44, 3.46     |
|qsec     |numeric |16.46, 17.02, 18.61, 19.44, 17.02, 20.22 |
|vs       |numeric |0, 0, 1, 1, 0, 1                         |
|am       |numeric |1, 1, 1, 0, 0, 0                         |
|gear     |numeric |4, 4, 4, 3, 3, 3                         |
|carb     |numeric |4, 4, 1, 1, 2, 1                         |

试试这个：

m = sapply(mtcars, typeof)

结果：

> m
     mpg      cyl     disp       hp     drat       wt     qsec       vs       am     gear     carb 
"double" "double" "double" "double" "double" "double" "double" "double" "double" "double" "double"

或者使用lapply：

m = data.frame(lapply(mtcars, typeof))

结果：

> m
     mpg    cyl   disp     hp   drat     wt   qsec     vs     am   gear   carb
1 double double double double double double double double double double double