Use column index instead of name in group_by

Question

I want to summarize a dataframe with dplyr, like so:

> test <-data.frame(ID = c(\"A\", \"A\", \"B\", \"B\"), val = c(1:4))
> test %>% group_by(ID         


        

Answer 1

You can use one of the scoped variants (group_by_at) for this:

test %>% group_by_at(1) %>% summarise(av = mean(val))

# A tibble: 2 x 2
#      ID    av
#   
#1      A   1.5
#2      B   3.5