Apply several summary functions on several variables by group in one call

Question

I have the following data frame

x <- read.table(text = \"  id1 id2 val1 val2
1   a   x    1    9
2   a   x    2    4
3   a   y    3    5
4   a   y    4            


        

Answer 1

Another dplyr option is across which is part of current dev version

#devtools::install_github("tidyverse/dplyr")
library(dplyr)

x %>% 
  group_by(id1, id2) %>% 
  summarise(across(starts_with("val"), list(mean = mean, n = length)))

Result

# A tibble: 4 x 4
# Groups:   id1 [2]
  id1   id2   mean$val1 $val2 n$val1 $val2
            
1 a     x           1.5   6.5      2     2
2 a     y           3.5   7        2     2
3 b     x           2     8        2     2
4 b     y           3     6        2     2

---

packageVersion("dplyr")
[1] ‘0.8.99.9000’