group_by by a vector of characters using tidy evaluation semantics

问题

I used to do it, using group_by_

library(dplyr)
group_by <- c('cyl', 'vs')
mtcars %>% group_by_(.dots = group_by) %>% summarise(gear = mean(gear))

but now group_by_ is deprecated. I don't know how to do it using the tidy evaluation framework.

回答1:

There is group_by_at variant of group_by:

library(dplyr)
group_by <- c('cyl', 'vs')
mtcars %>% group_by_at(group_by) %>% summarise(gear = mean(gear))

Above it's simplified version of generalized:

mtcars %>% group_by_at(vars(one_of(group_by))) %>% summarise(gear = mean(gear))

inside vars you could use any dplyr way of select variables:

mtcars %>%
    group_by_at(vars(
        one_of(group_by) # columns from predefined set
        ,starts_with("a") # add ones started with a
        ,-hp # but omit that one
        ,vs # this should be always include
        ,contains("_gr_") # and ones with string _gr_
    )) %>%
    summarise(gear = mean(gear))

回答2:

Transform the character vector into a list of symbols and splice it in

df %>% group_by(!!! syms(group_by))

来源：https://stackoverflow.com/questions/44984428/group-by-by-a-vector-of-characters-using-tidy-evaluation-semantics