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

In older versions of dpylyr, You could use standard evaluation with dplyr::group_by_:

test %>% 
 group_by_(names(.)[1]) %>% 
 summarize(av = mean(val))
## A tibble: 2 x 2
#      ID    av
#   
#1      A   1.5
#2      B   3.5